FR2688726A1 - Device for shaping a laser beam output from an optical fibre, with influx of assistance gas and suction of the smoke (fumes) and the slag - Google Patents

Abstract

The invention relates to devices for shaping a laser beam at the output of an optical fibre, these devices being furthermore provided with a nozzle for blowing in assistance gas and with a nozzle for sucking up the smoke and particles produced by the interaction of the laser with the material surface exposed. In an advantageous arrangement, the optical system (2), placed at the end of the optical fibre (8), is located in the tube (1) into which the gases are blown, so as to place the final lens (2) at a slight overpressure with respect to the external environment, and the suction takes place in the annular space formed between the tube (1) and the tube (3), the latter tube moreover constituting the mechanical case for the device. The device according to the invention may be used manually or at the end of a robot arm, as a cutting or scarfing (descaling) head.

Description

TECHNICAL DESCRIPTION
The present invention relates to devices for shaping a laser beam at the outlet of an optical fiber allowing the reuse of this beam for cutting, welding, cleaning, engraving or any other power application.

 It therefore appears to devices generally called "optical head". More specifically, the invention relates to the devices described above but also provided with integrated gas suction and blowing nozzles.

Beam recovery systems at the output of optical fiber are widely described or envisaged in numerous documents. Among these, some provide a supply of gas, generally oxygen, air or nitrogen as a gas to assist cutting.

Thereafter, we will simply call "optical head" these devices for shaping a laser beam at the exit of an optical fiber allowing the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other power application.

Thus, American patent 4,564,736 describes a "handpiece" allowing the focusing of the beam at the exit of optical fiber, and the optional contribution of a gas using a pipe connected at the end of the head. and allowing an almost axial ejection of the gas.

It is the same for the device decnt in the German patent 2,145,921 which foresees, him, a blowing of the gas in a perfectly coaxial way with the fiber, by using the flexible tube which sheaths the fiber as means of gas supply. The gas is introduced into the pipe at the level of the laser injection chamber into the fiber.

American patent 4,368,080 describes an optical head suitable for CO2 lasers and provided with both a suction and a blowing of protective gas. The latter is introduced directly into the focusing chamber; upstream of the last lens, while the aspiration is done through a bellows coaxial with the focusing body.

All of these devices, however, suffer from a certain number of drawbacks and impossibilities.

Thus, the German patent 2,145,921 does not provide for suction of gases and interaction products, the American patent 4,654,736 does not provide for suction either, and does it require the simultaneous displacement of the pipe sheathing of the fiber and the gas supply pipe, and finally American patent 4,368,080 does not provide for the use of an optical fiber and does it require the simultaneous displacement of sheathing tubes of the beam, d '' a gas supply pipe and a suction pipe.

The impossibility that there is in all of these patents to suck up almost all of the gases and particles produced by the action of the laser on the surface of the exposed material is particularly troublesome when the application consists in removing a part by laser. contaminated in order to extract the contaminated dust.

The other impossibility that there is in all these patents to protect the lens by a slight overpressure is particularly harmful to the intensive use of the head when the interaction of the beam with the surface of the exposed material produces a lot of smoke and particles solid.

The device according to the invention makes it possible to avoid these drawbacks and impossibilities since it ensures the five functions: optical shaping of the beam, supply of gas, aspiration, compactness which makes it possible to manipulate it by hand or to easily robotize the displacements, modular design which allows easy exchange of optics to adapt to applications.

The invention relates to a device for shaping a laser beam at the outlet of an optical fiber (8) allowing the use of this beam for cutting, welding, cleaning, engraving, or any other application of power comprising:
an optic (2) for taking up the beam at the fiber outlet (8) making it possible to give it given divergence and cross-section characteristics, a mechanical device (16) for holding the optical fiber (2) so that its exit face either rigidly linked to the optical system (2), a mechanical box (17) protecting the optics (2) and the device (16) for holding the optical fiber (8) and allowing manual or robotic gripping of the device, a hose (7) sheathing the optical fiber (8) and connected to the housing (17), and characterized in that it is further provided with a nozzle (18) for blowing gas of suitable shape and another (19 ) suction of the same gas and of any material originating from the interaction of the laser beam with the exposed material, connected to pipes (9) and (20) themselves connected to suitable means for blowing and suction.

According to another characteristic, the blowing nozzle (18) and the suction nozzle (19) are non-coaxial with the bundle, fixed inside or outside the mechanical housing.

According to another characteristic, one of the two blowing (18) or suction (19) nozzles is coaxial with the bundle.

According to another characteristic, the two blowing (18) and suction (19) nozzles are coaxial with the beam, the various flows being channeled in coaxial tubes, the smallest (1) therefore containing the laser beam, and the larger (3) which can advantageously be the housing (17) itself.

According to another characteristic, the gas under pressure is blown through the tube of smaller diameter (1), and in that the gas and any material originating from the interaction of the laser beam are sucked into the annular space delimited by the two pipes (1) and (3), so that the face of the lens (2) located closest to the outlet end of the device is slightly overpressured with respect to the external environment.

According to another characteristic, the gas under pressure is sucked through the tube of smaller diameter (1), and in that the gas and any material originating from the interaction of the laser beam are blown into the annular space delimited by the two pipes (1) and (3).

According to another characteristic, the suction flow rate is sufficiently greater than the blowing flow rate so that all of the blown gas, of the gases and of the particles possibly produced by the interaction of the laser beam with the material, are re-aspirated by the device and thus do not pollute the outside environment.

According to another characteristic, the suction pipe (20) is also the fiber sheathing pipe (7), and in that the blowing pipe (9) is introduced inside this pipe (7). cladding.

According to another characteristic, the blowing pipe (9) is also the fiber sheathing pipe (7), and in that the suction pipe (20) is introduced inside this sheathing pipe (7) .

According to another characteristic: the central tube (1) in which the gas is blown is machined so that it supports the single lens (2) constituting the optical system, the tube (1) is centered in the outer tube ( 3) by means of wings (4) and a thread (5), so that one can easily pass from one application to another, by unscrewing the tube (1) to replace it by another fitted with the new optical system, gases and particles are sucked between the two tubes (1) and (3) passing between the wings (4) of the tube (1) located at the front of the device, then between the wings (6 ) of the tube (3), which wings (6) support the thread rod (5) around which the tube (1) is screwed, then enter the pipe (7) which connects the device to the laser and to the means suction and blowing, and which protects the optical fiber (8), the pressurized gas is brought to the device using a plastic tube (9) of small section which connects to a metal end piece (10) welded in the thickness of one of the wings (6) of the tube (3), passes through a channel (10) pierced in this wing, opens into an annular space (11) which allows pass it through a metal tube (12) opening through the tube (1) whatever the relative angular position of the tubes (1) and (3), finally opens inside the tube (1) in front of the lens (2) through) an opening in which the tube (12) is slid, the optical fiber (8) is slid in a bore (13) formed in the central part of the tube (3) where the wings (6) are connected , and in particular through the threaded rod (5), and held stationary by means of an O-ring (14) tightened in its conical seat using a drilled screw (15), so that its face front is located at the level that the end of the threaded rod (5),
the pipe (9) is connected to the tube (10), and the optical fiber (8) is slid into the bore (13) then tightened by the screw (15), separating the pipe (7) from the tube (3) to which it is normally fixed by playing on its elasticity.

The characteristics and advantages of the invention will emerge more clearly from the description which follows, referenced in the appended drawings, in which:
FIG. 1 represents the device in its version in which the two nozzles are noncoaxial with the optical axis, and where (2) represents the optics, (7) the fiber sheathing pipe, (8) the optical fiber, (9) the blowing hose, (16) the fiber blocking system, (17) the housing, (18) the blowing nozzle, (19) the suction nozzle and (20) the suction hose .

Figure 2 shows the device in its version in which only the blowing nozzle is coaxial with the optical axis, and where (2) represents the optics, (7) the fiber sheathing pipe, (8) the fiber optic, (9) the blowing hose, (16) the fiber blocking system, (17) the housing, (18) the blowing nozzle, (19) the suction nozzle and (20) the hose aspiration.

FIG. 3 represents the device in its version in which the two nozzles are coaxial with the optical axis, and where (1) represents the blowing nozzle, (2) the optics, (3) the suction nozzle, ( 7) the fiber cladding pipe, (8) the optical fiber, (9) the blowing pipe, (16) the fiber blocking system, (17) the housing and (20) the suction pipe .

FIG. 4 and its different views represents the device in its version in which the two nozzles are coaxial with the optical axis, and in which in addition the sheathing pipe of the optical fiber is also the suction pipe, and where ( 1) represents the blowing nozzle, (2) the optics, (3) a suction nozzle, (4) the wings of the tube (1), (5) the threaded rod, (6) the wings of the tube ( 3), (7) the fiber cladding pipe, (8) the optical fiber, (9) the blowing pipe, (10) the wing piercing (6), (11) The annular space between the tube (1) and the threaded rod (5), (12) the communication pipe inside the tube (1) and the space (11), (13) the bore, (14) the seal and (15) the drilled screw.

The figures are given for information only, in order to. better understand the principle of the device, they are in fact in no way limiting and therefore do not detract from the generality of the invention.

The device according to the invention consists of an optic (2) for shaping the beam, a mechanical box (17), advantageously cylindrical, which contains the optic (2) and a fixing means (16) at the end of the fiber. The box is also connected to the fiber sheathing pipe (7). At its other end, the pipe is for example connected to the vacuum chamber which allows the beam to be injected into the fiber.

A pipe (9) through which pressurized gas arrives and another via which gases and the products of the interaction of the laser beam with the material leave have one end fixed to the housing (16), and are provided with a nozzle. (18) and (19) of suitable shape. Their other end is connected for one of the pipes (9) to a pressurized gas distribution system (bottle or compressor), and for the other (20) to a vacuum cleaner or a pump (Figure 1).

In an advantageous arrangement, the pipe (20) which sucks is also the one (7) which serves as a sheath for the optical fiber (8), which considerably simplifies the device. The pipe (9) which conveys the gas under pressure can either be connected to the device at the level of the head itself, in which case it is outside the sheathing pipe (7), or else be passed through the sheathing pipe ( 7) and therefore never be visible except near the injection chamber where it must be taken out of the cladding pipe to connect it to the bottle or the compressor (Figures 2, 3 and 4).

In another arrangement, the pipe (19) which blows the gas is also the one (7) which serves as a sheath for the optical fiber (8), which again considerably simplifies the device. In this case, it is the suction pipe (20) which can either be external to the sheathing pipe (7) of the fiber (8) and therefore connected to the device at the level of the head itself, or else internal to the hose (7) and therefore never be visible, except near the injection chamber where it must be removed from the sheathing hose (7) to connect it to the pump or the vacuum cleaner.

The circulation of the fluids in the device (blowing and suction) can advantageously be coaxial with the optical axis, which makes it possible to make their effects symmetrical on the surface exposed to the laser beam In this case, n of the flows pass through a tube of small diameter (1) which can advantageously contain the beam, while the other flow passes between this tube (1) and a second tube (3) of larger diameter which can advantageously also constitute the protective casing. it is then preferable that in the inner tube (1) which also contains the laser beam, pass the gas under pressure rather than the suction so that there reigns a slight overpressure protecting the front face of the last lens (2) projections of particles and condensations of gases produced by interaction.

This coaxial structure obviously requires a particular mechanical arrangement which allows both the mounting and the maintenance of the inner tube (1) and of the optics (2) with the outer tube (3), and the free passage of gases in the annular space delimited by the inner tube (1) and the outer tube (3).

In an advantageous design, the outer tube (3) supports wings (6) which are connected to the center of the tube in the form of a cylinder which will be called hub, provided at the front of the device, with a threaded rod (5), and at the rear, a thread. n is also crossed by a bore (13) of the same diameter as the optical fiber (8). The latter is blocked with a pierced screw (15), which is screwed into the thread of the hub, and which crushes an O-ring (14) in a cone machined in the hub, at the bottom of the thread.

We make sure that the end of the fiber (8) is located at the front end of the hub.

The optical system (2) is placed in the inner tube (1), and the latter is screwed onto the threaded rod (5) of the hub. The end of this tube located at the front of the device can be provided with wings (4) so that it can be easily centered in the external tube (3).

The aspirated gases pass into the annular space delimited by the inner tube and the outer tube, on either side of the wings of the inner tube and the outer tube.

The blown gases are injected into the inner tube (1), in front of the last lens (2), by a small pipe (12) which passes between the two tubes (1) and (3) and which communicates with an annular space formed between the threaded rod (5) and the outer tube (3). This annular space communicates with the rear of the device by a bore (10) formed in one of the wings (6) of the outer tube, itself connected to the flexible pipe (9) for supplying pressurized gas.

This provides a stripping head of small dimensions, all of whose functions are integrated within the same volume, without pipes to be moved other than that (7) of the sheathing of the fiber (8). The latter therefore contains the optical fiber (8) and the flexible pipe (9) for supplying pressurized gas. The suction is done directly through this sheathing pipe (7). It can be handled either by hand, holding it like a pencil or an electric torch, or by means of a robotic system.

In addition, it is easy to remove the tube (1) by simply unscrewing it from the threaded rod (5). It is thus possible to change the focusing optic to change the application: focused beam for cutting or pickling very thick, parallel beam for pickling, with a diameter fixed by the power density required by the application.

The device can be used to cut, engrave, weld or perform surface treatments by laser, and in particular using Nd: YAG lasers for which the joint use of an optical fiber is well known.

The device according to the invention furthermore lends itself particularly well to another application of Nd: YAG lasers, that is pickling or cleaning by laser. This technique, widely described in patent PCT / FR90 / 00037, requires good suction, and in particular when the pickling products are contaminated by radioactive dust or by chemically dangerous products. In this case, it should be ensured that the suction flow is greater than or equal to the flow supplied by the head itself (which can be canceled in this application, or made very low for the simple purpose of protecting the lens) to which is added the air flow taken from the external environment.

Claims (10)

1. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing the use of this beam for cutting, welding, cleaning, etching, or any other power application comprising: . an optic (2) for taking up the beam at the fiber outlet (8) making it possible to give it given divergence and cross-section characteristics,. a mechanical device (16) for holding the optical fiber (2) so that its outlet face is rigidly linked to the optical system (2),. a mechanical box (17) protecting the optics (2) and the device (16) for holding the optical fiber (8) and allowing manual or robotic gripping of the device, a pipe (7) sheathing the optical fiber (8) and connected to the housing (17), and characterized in that it is further provided with a nozzle (18) for blowing gas of suitable shape and another (19) for suction of the same gas and any material originating from the interaction of the laser beam with the exposed material, connected to pipes (9) and (20) themselves connected to suitable blowing and suction means. 2. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing the use of this beam for cutting, welding, cleaning, etching or any other power application according to claim 1 characterized in that the blowing nozzle (18) and the suction nozzle (19) are non-coaxial with the bundle, fixed inside or outside the mechanical housing. 3. Device for shaping a laser beam at the output of an optical fiber (8) allowing the use of this beam for cutting, welding, cleaning, engraving or any other power application according to claim 1 characterized in that one of the two blowing (18) or suction (19) nozzles is coaxial with the bundle.  4. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing  the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other  power application according to claims I and 3 characterized in that the two nozzles of  blowing (18) and suction (19) are coaxial with the bundle, the different flows being  channeled in coaxial tubes, the smallest (1) therefore containing the laser beam, and the most  large (3) which can advantageously be the housing (17) itself.  5. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing - the use of this beam for cutting, welding, cleaning, engraving or any other  power application according to claims 1, 3 and 4 characterized in that the gas is blown  under pressure through the tube of smaller diameter (1), and in that we suck the gas and all  material from the interaction of the laser beam in the annular space defined by the  two pipes (1) and (3), so that the face of the lens (2) located closest to the end of  outlet of the device is slightly overpressure relative to the external environment.  6. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing  the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other  power application according to claims 1, 3 and 4 characterized in that the gas is sucked  under pressure through the smaller diameter tube (1), and blowing the gas and all  material from the interaction of the laser beam in the annular space defined by the  two pipes (1) and (3).  7. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing  the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other  power application according to claims 1, 3, 4 and 5 or 1, 3, 4 and 6 characterized in  that the suction flow is sufficiently higher than the blowing flow so that all of the gas  blown, gases and particles possibly produced by the interaction of the laser beam with  matter, are re-aspirated by the device and thus do not pollute the outside environment.  8. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing  the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other  power application according to claims 1, 3, 4 and 5 characterized in that the hose  suction (20) is also the hose (7) for sheathing the fiber, and in that the hose (9) for  blowing is introduced inside this sheathing pipe (7).  9. Device for shaping a laser beam at the outlet of an optical fiber (8) allowing  the use of this bundle for cutting, welding, cleaning, engraving or any other power application according to claims 1, 3, 4 and 5 characterized in that the blowing pipe (9) is also the pipe (7 ) of sheathing of the fiber, and in that the suction pipe (20) is introduced inside this pipe (7) of sheathing. 10. Device for shaping a laser beam at the outlet of an optical fiber allowing the use of this beam for the purposes of cutting, welding, cleaning, engraving or any other power application according to claims 1, 3 , 4, 5 and 8 characterized in that:. the central tube (1) in which the gas is blown is machined so that it supports the single lens (2) constituting the optical system,. the tube (1) is centered in the outer tube (3) by means of wings (4) and a thread (5), so that Von can easily pass from one application to another, by unscrewing the tube (1) to replace it with another fitted with the new optical system,. the gases and particles are sucked between the two tubes (1) and (3) passing between the wings (4) of the tube (1) located at the front of the device, then between the wings (6) of the tube (3) , which wings (6) support the threaded rod (5) around which the tube (1) is screwed, then enter the pipe (7) which connects the device to the laser and to the suction and blowing means, and which protects the optical fiber (8),. the pressurized gas is brought to the device using a plastic tube (9) of small section which connects to a metal end piece (10) welded in the thickness of one of the wings (6) of the tube (3), passes through a channel (10) pierced in this wing, opens into an annular space (11) which allows it to pass through a metal tube (12) opening through the tube (l) whatever the relative angular position of the tubes (I) and (3), finally opens inside the tube (1) in front of the lens (2) through) an orifice in which the tube (12) is slid,. the optical fiber (8) is slid into a bore (13) formed in the central part of the tube (3) where the wings (6) are connected, and in particular through the threaded rod (5), and held stationary by means an O-ring (14) tightened in its conical seat using a drilled screw (15), so that its front face is located at the level that the end of the threaded rod (5),. the pipe (9) is connected to the tube (10), and the optical fiber (8) is slid into the bore (13) then tightened by the screw (15), separating the pipe (7) from the tube (3) to which it is normally fixed by playing on its elasticity.