Methods for cutting metal workpieces

Abstract

This application relates to a flatbed laser cutting machine (1). The flatbed laser cutting machine (1) has a workpiece support that defines a horizontal support area for a workpiece (5). The flatbed laser cutting machine (1) further has a laser cutting head (210) positioned above the support area, which emits a laser cutting beam (3) toward the workpiece (5) supported by the workpiece support, and is configured to move horizontally relative to the workpiece (5) and the workpiece support. Furthermore, the flatbed laser cutting machine (1) includes an energy recovery device (50) having a recovery structure below the support area, which is configured to recover the radiation energy of the laser radiation that travels from the laser cutting head (211) without being affected by the workpiece (5), and / or the radiation energy of the laser radiation that originates from the laser cutting head (211) and is reflected by the cutting front surface area. The energy recovery device (50) is configured to regenerate the radiation energy recovered by the recovery structure.

Description

Technical Field

[0001] The present invention is in the field of flat-bed laser cutting machines.

Background Art

[0002] A flat-bed laser cutting machine typically defines a horizontal support area and includes a workpiece support portion thereon for supporting a workpiece, which can be, for example, a sheet or plate of a material to be cut. The flat-bed laser cutting machine further includes a laser cutting head configured to emit a laser cutting beam in a direction perpendicular to the support area. The laser cutting head is configured to move at least in two horizontal directions with respect to the workpiece support portion to perform a desired cut.

[0003] In more recent years, there seems to be a significant increase in the demand for laser outputs exceeding 1 kW, for example, much larger laser outputs far exceeding 1 kW. However, it can be observed that only a small portion of the laser light output is actually coupled into the workpiece to locally melt or burn the material of the workpiece, that is, only a small portion of the energy can be actually used for cutting. Therefore, the energy efficiency of flat-bed laser cutting machines is very low, and it would be desirable to increase this efficiency.

[0004] Japanese Patent Application Laid-Open No. 2016-034649 discloses a laser beam cutting machine having a brush support portion or a roller support portion. This laser beam cutting machine has a laser cutting head movable in one horizontal direction (Y) such that the laser cutting beam extends in a plane (Y-Z plane), the workpiece support portion has a slit 21 extending in this plane, and a box 9 for cut pieces is below this slit. The workpiece W is movable in another horizontal direction (X) on the workpiece support portion. Japanese Patent Application Laid-Open No. 2016-034649 does not address any measures to address the problems associated with the increasing demand for even larger laser outputs in laser cutting machines.

[0005] U.S. Patent Application Publication No. 2015 / 0224601 relates to a method for recovering unused photoradiation energy from a machining apparatus. It is based on the idea of ​​converting radiation energy that is not absorbed by the workpiece and is trapped in a beam trap into electrical energy, for example, by photovoltaic means, or by a heat engine and generator. A beam trap is generally a hollow structure that allows the radiation from a beam to enter through a small light entry opening, but prevents the radiation from escaping due to the interaction between its geometric structure and a suitable covering. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-034649 [Patent Document 2] U.S. Patent Application Publication No. 2015 / 0224601 [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide a flatbed laser cutting machine that overcomes the shortcomings of conventional flatbed laser cutting machines. In particular, the object of the present invention is to provide a flatbed laser cutting machine in which the overall energy efficiency is improved when operated at a higher laser output. [Means for solving the problem]

[0008] This objective is achieved by a flatbed laser cutting machine having a workpiece support that defines a horizontal support area on which a workpiece, such as sheet metal or a metal plate, rests. The flatbed laser cutting machine further comprises a laser cutting head equipped to emit a laser cutting beam toward the workpiece supported by the workpiece support, for example, in a direction substantially perpendicular to the support area, and in addition, to emit a cutting gas (sometimes referred to as “auxiliary gas”) toward the workpiece, in particular toward the position where the laser cutting beam enters the workpiece. The laser cutting head is positioned above the support area and is generally equipped to move horizontally with two degrees of freedom (i.e., in one group of embodiments, if the z direction is defined as the direction of the laser beam, the laser cutting head can move in the x and y directions). The flatbed laser cutting machine further comprises an energy recovery device positioned and equipped to recover the radiation energy of the laser radiation traveling from the laser cutting head unaffected by the workpiece and / or the radiation energy of the laser radiation originating from the laser cutting head and reflected by the cutting front surface area, the energy recovery device being equipped to regenerate the radiation energy recovered by the recovery structure.

[0009] The radiation energy that strikes a workpiece is either absorbed or reflected by the workpiece. Only absorbed radiation can locally heat the workpiece and contribute to the cutting effect. Many metals being cut are often highly reflectable, which increases the proportion of reflected radiation. One insight underlying this invention is that, for reasons explained in more detail below, most of the reflected radiation is reflected downwards, and the thicker the workpiece, the greater the proportion of radiation reflected downwards. Furthermore, with a thicker workpiece, the direction in which the radiation is reflected becomes closer to vertical. Moreover, with a thicker workpiece, the proportion of absorbed radiation decreases. In addition, in reality, the speed at which the laser beam moves relative to the workpiece does not correspond to the ideal speed, but is lower, and as a result, some of the laser radiation propagates straight downwards without interacting with the workpiece at all.

[0010] In some embodiments, the direction of emission of the laser cutting beam may be vertical.

[0011] As described above, in some embodiments, the laser cutting head is configured to move in at least two horizontal directions, and the laser cutting beam is emitted downward toward the workpiece, for example, vertically, and the cutting gas is blown toward the workpiece toward the point of incidence. "Emitted downward" does not preclude the laser cutting beam from traveling at an angle other than 90° with respect to the horizontal, for example, if the laser cutting head is configured to be tilted vertically. However, in embodiments, the laser cutting head is designed so that the laser cutting beam is emitted vertically.

[0012] As is well known in laser processing, the fact that a laser cutting head is equipped to emit a laser cutting beam and moves horizontally does not preclude it from moving even when the beam is not being emitted at all, for example, to move to the position where cutting will begin (the drilling position).

[0013] In embodiments in which the laser cutting head can move in two horizontal directions, the workpiece can still be placed on the workpiece support and does not need to be moved. This is advantageous in terms of handling, especially when the workpiece is large in size, at least initially, and also in terms of achievable cutting speed. Even in such situations, it is meaningful and possible to recover and regenerate the energy emitted downwards towards the workpiece, which is an insight of the present invention.

[0014] When the laser cutting head moves in two horizontal directions, the laser radiation energy emitted downwards from the workpiece can incident on a relatively large area; therefore, according to the first method, the recovery structure extends downwards from the workpiece to cover a wide area. In some examples, the recovery structure may include a container that opens downwards from the workpiece. Such an open container will receive the cutting waste blown downwards by the release of the processing gas. As will be described in more detail herein, the machine may be equipped to carry away such cutting waste. In other examples, the machine may include a moving structure such as a cooled conveyor. According to the second method, the recovery structure may be movable and may be equipped to move in conjunction with the movement of the laser cutting head, particularly in one of the horizontal directions, and may extend in the other horizontal direction.

[0015] The processing gas emitted toward the workpiece plays a supporting role in the laser cutting process. The processing gas performs these functions by blowing away the molten workpiece material at the cutting surface downwards and by cooling the workpiece in direct proximity to the point where the laser cutting beam enters. If the processing gas contains oxygen, it may also provide additional support by generating heat at the point of entry (reactive laser cutting).

[0016] The flatbed laser cutting machines described herein may be equipped to emit a laser having an output of at least 1 kW, and in particular at least 5 kW or at least 10 kW.

[0017] High-power laser cutting machines are particularly used for cutting thick workpieces. Therefore, the above insights reveal that high-power laser cutting machines not only have greater power output, but also a greater proportion of the power that is unused and radiated downwards towards the support area.

[0018] This is why the recovery structures located below the support area are particularly valuable.

[0019] To regenerate the recovered radiation energy, the energy recovery device is equipped with corresponding energy regeneration equipment.

[0020] In this case, regeneration may include directly or indirectly converting radiation energy into electrical energy.

[0021] As an example of direct conversion, the recovery structure may include an energy recovery facility comprising a photocell and / or reflector, and the photocell positioned such that the radiation reflected by the reflector strikes the photocell. In this case, in order to maintain the energy density on the surface of the photocell within a reasonable range, the reflector may be configured, for example, to induce diffuse reflection and disperse the residual laser radiation energy over a relatively wide area.

[0022] Indirect conversion to electrical energy may include heating the recovery structure (or, if the recovery structure is equipped with a reflector, the structure to which the reflected radiation energy hits) by exposing it to the radiation energy. The heat can then be converted into electrical energy by a heat engine and generator, or by a thermoelectric converter (thermogenerator) such as a Peltier element (also called a Seebeck generator) that uses the Seebeck effect.

[0023] Nor can all heat caused by radiation be converted into electrical energy by both direct and indirect conversion. The remaining heat can optionally be used directly for heating, hot water production, etc., including the possibility of storing the heat in a heat accumulator for later use. Alternatively, the remaining heat can be dissipated, for example, by cooling water or by a structure having cooling ribs.

[0024] As an alternative to being used for conversion to electrical energy, heat may be used directly only for heating, hot water production, etc. This includes the possibility of storing the heat in a heat accumulator for later use.

[0025] All combinations of options are possible. In one example, radiation first strikes a photovoltaic cell through a reflector. Next, the heat generated by the photovoltaic cell and / or the heat generated in the secondary recovery structure and / or the heat generated in the reflector by the radiation reflected by the photovoltaic cell can be recovered by a recuperator fluid and supplied to an indirect conversion device. The remaining heat that has not been converted but accumulates, for example, in a refrigerant circuit that cools the indirect conversion device can be used directly for heating, etc. In another example, the photovoltaic cell can be arranged peripherally with respect to the recovery structure, the recovery structure is provided to absorb the main part of the radiation, and the photovoltaic cell is arranged to recover the part of the radiation not absorbed by the recovery structure.

[0026] In both direct and indirect conversion, and when heat is directly utilized, the energy recovery device may be configured such that the recuperator fluid, particularly a liquid, and therefore a coolant, is in contact with the recovery structure. The recuperator fluid can carry away heat in such a way that the machine can be configured to transport the recuperator fluid from the recovery structure. For example, the recuperator fluid can be transported to an energy recovery facility, such as a facility for indirectly converting to electrical energy as described above. In addition to transporting the coolant to an energy recovery facility, or as an alternative, the machine may transport the recuperator fluid to a heat storage unit and / or heat exchanger for direct heat utilization.

[0027] Whether or not an energy recovery system is present, using a main recuperator fluid circuit and a secondary recuperator fluid circuit with a heat exchanger in between is one option. A main recuperator fluid circuit in contact with the recovery structure and a secondary recuperator fluid circuit in contact with the energy recovery system, heat storage unit, or heat exchanger may be particularly beneficial in embodiments where the (main) recuperator fluid may be exposed to contamination, but the benefits may not be limited to this.

[0028] In the energy recovery scheme used, it is also an option to include cooling of the laser source itself and / or the pumping source, if the laser is optically pumped. For example, the recuperator fluid before contact with the recovery structure can cool the laser source and / or the pumping source, thereby preheating the recuperator fluid, especially when a converter that is a heat engine is used.

[0029] The recovery structure will have a physical shape and orientation that will be suitable for recovering the radiation energy of the laser radiation.

[0030] According to the first group of embodiments, the cooling equipment and recovery structure extend below the support area to cover a relatively large portion of the support area, for example, substantially the entire support area. More precisely, this means that the projection of the support structure onto the support area along the z-direction (i.e., opposite to the direction in which the laser beam propagates) covers a large portion of the support area, for example, at least 60%, at least 70%, at least 80%, or at least 90%. In this case, the support area is defined as the area in a plane that can be placed on a workpiece and extends horizontally to all places where the laser beam can advance to cut into the workpiece, and therefore the area that can be processed by the laser cutting beam.

[0031] The fact that the recovery structure extends below the support area and covers a relatively large portion of it implies that, regardless of where the laser head is moved relative to the workpiece, there is a high probability that radiation emitted in the z-direction through the support area will hit the recovery structure. This, combined with the above insight that unabsorbed radiation is mainly emitted straight downwards, essentially in the z-direction, ensures that the main portion of unabsorbed radiation can be recovered and the base of the machine protected.

[0032] Examples of embodiments of the first group include, for example, a container having a recuperator fluid. Such a container is, for example, insertable and retractable with respect to the base of a machine. In some embodiments, the container may be configured by a trolley. Such a container located below a support area, and the recuperator fluid itself if it absorbs radiation, also belong to the recovery structure. Such an arrangement is simple to implement. However, if the container is open on the top, cutting waste accumulates in the container, and as a result, embodiments with such an open container require good filtration and frequent replacement of the recuperator fluid.

[0033] Further embodiments of the second group include a recovery structure comprising a conveyor equipped to continuously or intermittently carry away cutting waste from below a support area.

[0034] In the first subgroup of embodiments, the container and conveyor ideas are combined such that the conveyor is at least partially immersed in a recuperating fluid. Cutting waste, which is in most cases denser than ordinary liquids (such as water), sinks into the container and is collected by the conveyor, thereby being transported out of the container. In addition to carrying away heat, the recuperating fluid also has the effect of preventing any non-solid pieces of cutting waste from coming into direct contact with the conveyor. In other words, the cutting waste is cooled by the recuperating fluid to a degree that allows it to exist as a solid when in contact with the conveyor, thereby ensuring that it does not adhere to the conveyor.

[0035] In the second subgroup of the first group of embodiments, the conveyor is not immersed in the recuperator fluid at the point where unabsorbed radiation strikes it. Rather, the remaining laser radiation, i.e., laser radiation not absorbed by the workpiece, strikes the conveyor directly (and / or indirectly via reflection), and the conveyor is heated. The recuperator fluid can also be used to carry heat away from the conveyor. For example, the conveyor may have a thermal contact structure that comes into contact with the recuperator fluid. In some embodiments, such a thermal contact structure comes into contact with the recuperator fluid bath, in which case there is no need for piping or anything similar to be linked to the movement of the conveyor. In some examples, the contact structure may consist of a projection of the conveyor and a recuperator fluid bath into which such projection or similar is immersed.

[0036] In the second group of embodiments, the recovery structure is not necessarily as extended as the processing area, and the recovery structure is a movable recovery structure, configured to cooperate with at least some of the movement of the laser head relative to the support area.

[0037] In particular, a flatbed laser cutting machine may include a bridge section on which a laser cutting head is mounted, the bridge section being able to move the laser cutting head in a first horizontal direction (x direction) relative to the bridge section. The bridge section as a whole is movable in a second horizontal direction (y direction) relative to the workpiece support section. This is a structure that is common in itself with respect to flatbed laser cutting machines. According to some embodiments of the second group of embodiments, a retrieval structure, which is a movable retrieval structure, is coupled to the bridge section and moves together with the bridge section in the y direction, i.e., in the positive and negative y directions.

[0038] In particular, in such embodiments, the (movable) recovery structure may include a liquid transport tube for transporting the recuperator fluid. This tube is essentially parallel to the x-axis and moves in the y-direction together with the bridge.

[0039] In some embodiments, such liquid transport tubes as recovery structures have a cross-section other than circular, while in other embodiments the cross-section is circular. In particular, the cross-section may be optimized so that cut waste does not adhere to the recovery structure. For example, the cross-section may have an edge on the upper side (and thus an angle in the cross-section perpendicular to the longitudinal extension of the liquid transport tube). In addition to this, or as an alternative, the horizontal extension in the cross-section (in the y-direction in the above example, and the cross-section is also a cross-section perpendicular to the longitudinal extension, corresponding to, for example, the cross-section in the yz-plane) may be smaller than the vertical extension.

[0040] The recovery structure in the above-described embodiment is configured to absorb the remaining laser radiation (or at least a large portion thereof) and convert it directly or indirectly into electricity and / or usable heat. The surface portion of the recovery structure can be provided as described above, for example by having a chemical composition that promotes the absorption of radiation at the wavelength of the laser beam and / or by having a corresponding structure, for example, a corresponding roughness. In embodiments in which radiation also directly strikes the recuperator fluid, the recuperator fluid can be appropriately stained, for example, to absorb the radiation.

[0041] In addition to absorbing unused radiation, or as an alternative to doing so, the recovery structure may include a reflective surface portion, for example, a photosensitive panel, that directs the radiation portion to an absorbing element of the energy recovery device. Such an absorbing element may, but is not necessarily, be located below the support area.

[0042] In addition to relating to a flatbed laser cutting machine, the present invention relates to a method of laser cutting a workpiece, in particular a metal workpiece, in particular a flat metal workpiece (hence sheet metal or metal plate) using the flatbed laser cutting machine disclosed herein, wherein the laser cutting is a method of moving a laser cutting head relative to the workpiece, with a laser cutting beam emitted toward the workpiece and a working gas blown toward the workpiece (of course, this does not preclude the possibility that the laser cutting head may also be moved at times when the laser beam is off, as is generally known in laser cutting). In particular, in some embodiments, the laser cutting beam may be emitted vertically and perpendicular to the (upper) surface of the workpiece, the recovery structure may be located vertically below the position where the laser beam enters the workpiece, and the working gas may be emitted toward the position where the laser beam enters the workpiece.

[0043] Embodiments of the present invention will be described in more detail below with reference to the drawings. In the drawings, the same reference numerals refer to the same or similar components. [Brief explanation of the drawing]

[0044] [Figure 1] This is a diagram of a flatbed laser cutting machine. [Figure 2] This is a cross-sectional view of the workpiece at the cutting surface. [Figure 3] This is a graph of the approximate absorption coefficient of steel for unpolarized light, as a function of the angle of incidence. [Figure 4] This is a cross-sectional view corresponding to the cross-sectional view in Figure 2, under non-ideal conditions. [Figure 5]This is a diagram of a flatbed laser cutting machine with a cooled machine base. [Figure 6] The image above shows a diagram of a trolley for a laser cutting machine. [Figure 7] This is a diagram illustrating the principle of a belt conveyor immersed in a recuperator fluid bath. [Figure 8] This is a diagram illustrating yet another embodiment of a belt conveyor having a recuperator fluid bath. [Figure 9] This is a diagram showing a modified example of the embodiment shown in Figure 8. [Figure 10] This figure shows a further variation of the embodiment shown in Figure 8. [Figure 11] This figure shows yet another variation of the embodiment shown in Figure 8. [Figure 12] This is a diagram of another embodiment of a flatbed laser cutting machine. [Figure 13] This is a cross-sectional view of the liquid transport tube according to the embodiment shown in Figure 12. [Figure 14] This is a cross-sectional view of the liquid transport tube according to the embodiment shown in Figure 12. [Figure 15] This is a cross-sectional view of the liquid transport tube according to the embodiment shown in Figure 12. [Figure 16] This is a cross-sectional view of the liquid transport tube according to the embodiment shown in Figure 12. [Figure 17] This is a diagram of yet another embodiment of a flatbed laser cutting machine. [Modes for carrying out the invention]

[0045] Figure 1 shows an example of a laser cutting machine 1. This machine comprises a laser source 201, a transmission fiber 212, a laser cutting head 210, and a laser cutting head movement mechanism. The workpiece 5 is supported by a workpiece support (not shown in Figure 1). The laser cutting head movement mechanism includes a bridge section 202 that allows the laser cutting head 210 to move in the x-direction relative to itself, and is itself movable in the y-direction relative to the processing table and the workpiece 5, for example, on a pair of rails. When the laser cutting head 210 is in operation and moved relative to the workpiece, it emits a laser cutting beam 3 substantially vertically downward on the workpiece to create a cut (cut edge 51). In addition, the laser cutting head 210 emits a gas jet 4 of processing gas toward the position where the laser beam 3 enters the workpiece 5. The workpiece 5 may be a metal plate that is cut by the laser cutting beam emitted by the laser cutting head.

[0046] During laser cutting, high-speed and high-acceleration motion is required in both the x and y directions within the machining area. The motion in the y direction involves moving the entire bridge section 202 together with the head.

[0047] Even when the laser beam strikes the support area (defined by the processing table and corresponding to the lower surface of the plate-shaped workpiece 5 in the illustrated embodiment) from a direction perpendicular to it, the angle of incidence is significantly greater than 0°. Figure 2 shows the cutting surface 53 as the laser cutting beam 3 moves relative to the workpiece 5 in the cutting direction 54. As can be seen from Figure 2, the minimum angle of incidence is α min =tan -1 (t / w) In this equation, t is the thickness of the workpiece and w is the width (average diameter) of the laser beam passing through the workpiece. For relatively thick workpieces, such as those typically cut by high-power laser beams, the minimum angle is relatively large. For example, if the width is w = 200 μm and the thickness t of the workpiece is 2 mm to 20 mm, the minimum angle is 84° to 89.5°. The maximum angle of incidence is 90° for geometric reasons.

[0048] The absorption coefficient is a material property that describes how much light energy a material can absorb. The degree of absorption depends on the angle of incidence, wavelength, and polarization, in addition to the material properties. Figure 3 shows the approximate absorption coefficient A of steel for unpolarized (or circularly polarized) light with wavelengths of 1 μm and 10 μm, as a function of the angle of incidence α. Clearly, the degree of absorption at angles of incidence such as those occurring during laser cutting is small, especially at the wavelength of 1 μm, and is always less than 40%. Particularly as the laser power increases, most of the very thick material is cut, and therefore only the portion with low laser power, significantly less than 10%, is absorbed. The remainder is reflected. By the law of reflection, and given that the cutting surface 53 is nearly vertical, the portion of the unabsorbed laser light travels substantially downwards.

[0049] However, in reality, the theoretically best minimum incidence angle does not occur. A typical cutting process is as shown in Figure 4, where a portion of the laser beam is radiated downwards to the bottom without interacting with the cutting surface 53, and the incidence angle α is α min It is even larger. This means that the yield of energy available for the separation process is even lower, the proportion of radiation energy radiated downward from the support area is even higher, and the direction is vertical (radiation not interacting with the workpiece) or nearly vertical (radiation reflected by the cutting surface), and therefore substantially vertical.

[0050] Figure 5 illustrates a first embodiment of the present invention. The laser cutting machine 1 has an energy recovery device 50 at the base of the machine for recovering thermal laser energy. The thermal laser energy recovered by the energy recovery device can be used beneficially by direct regeneration (as heat directly used for heating or as heat stored in a heat storage unit) or by conversion into electrical energy by a conversion device. In addition to energy acquisition, the machine base with a cooling device has the advantage of significantly lower wear on the machine base than state-of-the-art laser cutting systems. Wear on the machine base is considerably large, especially when the laser output is 30 kW or more, due to the thermal effect of the laser beam used for processing.

[0051] In the embodiment shown in Figure 5, the energy recovery device 50 is connected to a heat exchanger, which can then be connected to a generator to produce electricity, as will be described in more detail below. Figure 5 is a cross-section of a flatbed laser cutting machine of the type currently commonly used for laser cutting sheet metal.

[0052] The workpiece support is formed by a support grid 14. The support grid 14, along with the workpiece 5, lies horizontally beneath the laser cutting head 210, illustrated here with a nozzle 211 for firing a gas jet of cutting gas toward the position where the laser beam enters the workpiece 5. Below the support grid is the base of the machine, which includes a movable trolley 4 from which cutting waste falls. Unused laser power is absorbed by the base of the machine with the trolley 4. As schematically shown in Figure 6, the trolley, according to the illustrated embodiment, is part of the energy recovery device and may be equipped with a recuperator fluid. For this purpose, the trolley 4 includes an inlet 41 and an outlet 42 for the containers, each forming a container for the recuperator fluid, each fluid-connected to a tube.

[0053] During operation, the constant flow of a recuperator fluid, particularly water, ensures that the heat generated by the absorption of radiation by the trolley is recovered, carried away, and made available. The recuperator fluid can flow in an open or closed recuperator fluid circuit. If heat is needed to generate electricity, the tubes can pass through a heat exchanger, which is then connected to a generator to produce electricity. The generated electrical energy can be stored in a battery or directly fed back to the machine's grid or power supply.

[0054] In embodiments having a trolley forming the base of the machine, through which the recuperator fluid flows, the tubes supplying and discharging the recuperator fluid to the trolley must be long and flexible enough to allow the trolley to be removed periodically so that the trolley can collect the cutting waste that needs to be disposed of at regular intervals. For example, the machine may be equipped with a drum for tubes to neatly accommodate any excess tubes.

[0055] In a further group of embodiments, the base of the laser machine is equipped with a conveyor belt for carrying away cutting waste and cutting dust. The conveyor belt has the advantage that it eliminates the need to manually empty the cutting waste from the trolley.

[0056] Figure 7 schematically shows a machine having a belt conveyor for transporting cutting waste from a container holding recuperator fluid 72. For example, a conveyor belt 71 having metal segments is partially immersed in the recuperator fluid 72 bath. During operation of the laser cutting machine and / or between operating cycles, the conveyor belt can be operated to hold the recuperator fluid 72 bath and transport debris (cutting waste) from a container 73 located below the support area that constitutes the base or part of the machine. As in the embodiments of Figures 5 and 6, the thermal energy transferred by the recuperator fluid can be used, for example, to generate electricity. The recuperator fluid can be passed through a heat exchanger, which is then connected to a generator to produce electricity. The generated electrical energy can be stored in a battery or directly fed back to the machine's grid or power supply.

[0057] A further embodiment is described with reference to Figure 8. The machine comprises a belt conveyor. A cross-sectional view of the conveyor belt 71, which is cooled by a recuperator fluid, is shown in Figure 8. The conveyor belt 71 is cooled only from below by the recuperator fluid 72, such that cooling fins 75 on the inside of the conveyor belt 71 are driven via the recuperator fluid held by a container 73. In this way, the conveyor belt 71 is well cooled, but the cut waste does not fall into the recuperator fluid (e.g., water). The recuperator fluid inlet 41 and recuperator fluid outlet 42 ensure that the conveyor belt is constantly cooled and removed for heat utilization, as in the embodiments described above.

[0058] The embodiment illustrated with reference to Figure 8 has the additional advantage that cutting waste does not fall into the recuperator fluid bath. The machine may be equipped with an outer covering that effectively shields the bath from any waste, dust, etc. This is in contrast to the embodiment of Figure 7, in which the recuperator fluid can become seriously contaminated over time depending on the material being cut, and a mixture of coolant and dust can contaminate all parts of the machine that come into contact with it.

[0059] Figure 9 shows an even further variation. Similar to the embodiment in Figure 8, the conveyor belt 71 also generates heat to the recuperator fluid 72 on the side facing away from the workpiece support section formed by the support grid 14 (see Figure 5), with the assistance of, for example, cooling fins 75, so that the recuperator fluid 72 does not come into contact with the cutting waste. The recuperator fluid 72 is contained in a recuperator fluid container 73, which has a bottom that is a good thermal conductor, for example, at least the bottom of the container 73 may be sheet metal or another relatively thin material with good thermal conductivity. Directly below the container 73, in thermal contact with it, is a flat installation 78 of a thermoelectric converter in the form of a Peltier element 77 (in this specification, an element that uses the so-called Seebeck effect to convert heat into electrical energy is referred to as a "Peltier element"). The container 73 constitutes the high-temperature side of the Peltier element 77, while the cooling structure (not shown in Figure 9) constitutes the low-temperature side. The Peltier element converts the thermal energy absorbed by the recuperator fluid into electrical energy. The electrical energy is supplied to the energy storage device 80 via the electrical line 79. The electrical energy is not stored in the energy storage device 80, but can be supplied directly to the grid and / or reused directly by a laser cutting machine or other equipment.

[0060] The portion of thermal energy that cannot be converted into electrical energy can also be used at will. For example, the cooling structure on the low-temperature side of the Peltier element 77 may contain a liquid coolant, and the heat absorbed by the corresponding coolant (different from the recuperator fluid) can be used in the manner described above, for example, for heating purposes, to regenerate the cold side of a heat pump system.

[0061] More generally, the present invention also encompasses any possibility of utilizing thermal energy recovered below the support area (particularly below or even recovered by the workpiece support), including any possibility of converting thermal energy into electrical energy (i.e., converting thermal energy into electrical energy to the extent possible within physical and practical limits, while also having the option of using unavoidable waste heat recovered on the cold side of the conversion equipment).

[0062] Figure 10 shows a variation of the embodiment shown in Figures 8 and 9. A meandering line 81 for the secondary recuperator fluid is located inside the container 73, thereby extracting thermal energy from the recuperator fluid 72 inside the container 73. The meandering line 81 is connected to a generator unit 82, which generates electrical energy from thermal energy supplied, for example, by a steam turbine. This electrical energy is supplied to a power storage device 80 via an electrical line 79. Instead of the power storage device 80, a direct grid connection can be provided to supply electrical energy to the grid. The power storage device 80 can be connected to the power supply of the laser cutting system and supply energy to the power supply.

[0063] Figure 11 shows a further variation that combines the ideas of the embodiments described with reference to Figures 8, 9, and 10, namely, that electrical energy can be generated by both the Peltier element 77 and the generator 82. In Figure 11, line 81 for the secondary recuperator fluid is located on the high-temperature side of the Peltier element 77, and thus heat is supplied in parallel to both the Peltier element 77 and the generator 82. It would also be possible to have a series arrangement in which the secondary recuperator fluid that supplies heat to the generator 82 is used to cool the low-temperature side of the Peltier element 77, and / or the low-temperature side of the generator 82 (strictly speaking, the heat engine of the generator) is cooled by the Peltier element. In practice, this arrangement can be optimized based on the best operating temperature of the relevant components.

[0064] A further embodiment is shown in Figure 12. The bridge section 202 (see also Figures 1 and 5) is connected to a movable recovery structure in the form of a liquid transport tube 90.

[0065] A cross-section of the liquid transport tube 90 is shown in Figure 13. Laser radiation 3 that is emitted downwards without being utilized is collected by the liquid transport tube 90, thereby generating heat. The shape of the liquid transport tube 90 can be oval / elliptical so that pieces, dropped portions, and cutting waste can fall to the bottom without adhering to them. Figure 14 shows an alternative shape of the liquid transport tube 90, namely a triangle.

[0066] Figures 15 and 16 illustrate modified examples of embodiments of Figures 13 and 14, respectively, in which the liquid transport tube 90 comprises a body 91 of a first material and a covering 92 of a second material different from the first material, at least on the upper side. In this case, the first material may be a relatively ductile material that is a good thermal conductor and / or minimizes the possibility of tube breakage. Examples of suitable first materials include copper, aluminum, and steel. The second material may be a highly heat-resistant material such as ceramic.

[0067] Below the movable recovery structure, the laser cutting machine may be equipped with a conveyor belt or a trolley 4 for collecting and removing cutting waste.

[0068] In a modified example having a recuperator fluid transport tube that moves with the bridge section, the heat absorption unit is closer to the laser cutting head 210, thereby absorbing more energy and reducing the risk of damage even if waste falls from the cutting table. The total area of ​​the system is also reduced because the liquid transport tube follows the movement of the bridge section. This makes it easier to heat the recuperator fluid, and thus the heat engine or other power generation device can have higher efficiency, as the Carnot efficiency, which sets the upper limit of achievable efficiency, depends on the temperature difference between the high-temperature and low-temperature sides. Furthermore, although substantially all residual radiation (see previous descriptions herein) hits the energy recovery structure, there is no direct contact between the recuperator fluid 72 on the one hand and the cutting waste on the other.

[0069] Figure 17 shows an embodiment similar to the embodiment in Figure 12, having a liquid transport tube 90 as a movable recovery structure. In contrast to the latter, the laser cutting machine additionally has a photosensitive panel 92 positioned to receive radiation that is reflected, and in particular diffusely reflected, by the surface of the (movable) recovery structure.

[0070] Embodiments of the type shown in Figure 17, which involve directly converting unused laser radiation into electrical energy, advantageously have a structure that disperses the unused laser radiation over a wide area, thereby preventing excessive intensity at the conversion site, on the photosensitive panel 92 in Figure 17. This may be achieved, for example, by designing the surface of the recovery structure such that any reflection is diffuse by locally concave or convex the reflective surface portion. In this way, destruction or damage to the photosensitive panel 92 can be avoided.

[0071] Embodiments that include directly converting unused laser radiation into electrical energy may further include measures to prevent cutting material from being scattered onto the photosensitive panel. For example, a screen can be installed on the lower side of the processing area so that there is no direct path from the photosensitive surface of the photosensitive panel to the workpiece, on the one hand, where the laser beam enters the workpiece, and on the other hand, so that only reflected radiation reaches the photosensitive surface.

Claims

1. A flatbed laser cutting machine (1) having a workpiece support section that defines a horizontal support area for a workpiece (5), the flatbed laser cutting machine further comprising a laser cutting head (210) installed above the support area and configured to emit a laser cutting beam (3) toward a workpiece supported by the workpiece support section, and in addition to emitting a cutting gas toward the workpiece, and configured to move horizontally with respect to the workpiece (5) and the workpiece support section, wherein the flatbed laser cutting machine (1) is further characterized by a recovery structure provided below the support area, configured to recover the radiation energy of laser radiation that travels from the laser cutting head without being affected by the workpiece, and / or the radiation energy of laser radiation originating from the laser cutting head and reflected by the cutting front surface area (53), and configured to regenerate the radiation energy recovered by the recovery structure.

2. A flatbed laser cutting machine according to claim 1, characterized in that the energy recovery device is installed such that the recuperator fluid is in contact with the recovery structure.

3. A flatbed laser cutting machine according to claim 2, characterized in that it comprises an energy recovery unit which is provided for transporting the recuperator fluid from the cooling structure to the energy recovery unit and / or which is in contact with the recuperator fluid.

4. A flatbed laser cutting machine according to claim 3, wherein the energy recovery equipment comprises a heat engine for converting recovered heat into mechanical energy and a generator for converting the mechanical energy into electrical energy.

5. A flatbed laser cutting machine according to claim 3 or 4, wherein the energy regeneration equipment comprises a thermoelectric converter.

6. A flatbed laser cutting machine according to any one of claims 2 to 5, characterized in that it comprises a container (73) for the recuperator fluid located below the support area.

7. A flatbed laser cutting machine according to any one of claims 2 to 6, characterized in that it comprises a belt conveyor which constitutes at least a part of the recovery structure and is installed to carry away cutting waste from the area below the support area.

8. A flatbed laser cutting machine according to claim 7, characterized in that the upper surface of the conveyor belt (71) is not in contact with the recuperator fluid, and the conveyor belt (71) is provided with a thermal contact structure in thermal contact with the recuperator fluid.

9. A flatbed laser cutting machine according to any one of claims 1 to 8, further comprising a sub-recuperator fluid circuit, wherein the sub-recuperator fluid circuit has a heat exchanger between the recuperator fluid and its own sub-recuperator fluid.

10. A flatbed laser cutting machine according to any one of claims 1 to 9, wherein the recovery structure is immobile, extends below the workpiece support, and has a horizontal dimension substantially corresponding to the horizontal dimension of the workpiece support.

11. A flatbed laser cutting machine according to any one of claims 1 to 10, wherein the recovery structure comprises an open container.

12. A flatbed laser cutting machine according to any one of claims 1 to 9, wherein the recovery structure comprises a movable recovery structure that is coupled to the laser coupling head in conjunction with the movement of the laser cutting head.

13. A flatbed laser cutting machine according to claim 12, comprising a bridge section on which the laser cutting head (210) is mounted, wherein the laser cutting head is movable in a first horizontal direction (x) relative to the bridge section, the bridge section is movable in a second horizontal direction (y) different from the first horizontal direction relative to the workpiece support section, and the movable recovery structure is movable in the second horizontal direction (y) together with the bridge section (202).

14. A flatbed laser cutting machine according to claim 12 or 13, wherein the movable recovery structure comprises a liquid transport tube (90) for the recuperator fluid.

15. A flatbed laser cutting machine according to claim 14, characterized in that the liquid transport tube has a cross-section different from a circle, the cross-section is pointed upward, and at least one of the following conditions is met: the horizontal dimension of the cross-section is smaller than the vertical dimension.

16. A flatbed laser cutting machine according to any one of claims 1 to 15, wherein the energy recovery device comprises a photocell.

17. A flatbed laser cutting machine according to any one of claims 1 to 16, characterized in that the laser cutting head (210) is configured to emit the laser cutting beam (3) in a vertical downward direction.

18. A flatbed laser cutting machine according to any one of claims 1 to 17, wherein the laser cutting head (210) is configured to move in at least two horizontal directions (x, y), the laser cutting beam (3) is emitted downward toward the workpiece (5), and the cutting gas is blown toward the workpiece.

19. A method for laser cutting a workpiece (5), comprising: providing a flatbed laser cutting machine (1) according to any one of claims 1 to 18; moving the laser cutting head (210) relative to the workpiece, the laser cutting beam (3) being emitted toward the workpiece (5), and the processing gas being blown toward the workpiece (5).

20. A method according to claim 19, wherein the workpiece (5) is a sheet metal or metal plate and extends horizontally on the workpiece support, the laser cutting beam (3) is emitted vertically and incident perpendicularly to the surface of the workpiece, the recovery structure is located vertically below the position where the laser beam is incident on the workpiece, and the processing gas is emitted relative to the position on the workpiece (5) where the laser beam is incident.

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