Air-cooled carbon dioxide laser

Abstract

The carbon dioxide waveguide laser includes an elongated resonator unit and an elongated power supply unit. The resonator and the power supply unit are separated by a cooling unit comprising a plurality of longitudinally extending, spaced apart fins, and the fan is arranged to drive air through a space between the fins.

Description

[0001] The present invention is a divisional application of the invention patent with application number 2016800222502, application date March 30, 2016, and invention name “Air-cooled carbon dioxide laser”. Technical Field

[0002] The present invention relates generally to carbon dioxide (CO2) lasers which are energized by radio frequency (RF) discharge. In particular, the present invention relates to cooling arrangements for such lasers. Background Art

[0003] CO2 lasers are used in several precision laser machining operations, particularly the drilling of holes in various substrate materials. In this operation, the laser is operated in a pulsed mode and the output beam of the laser is driven by a galvanometer mirror to the location on the substrate where the hole is to be drilled.

[0004] The problem with all such lasers is that during the warm-up period when the laser is switched on after a quiescent period, the direction of the output beam, which is referred to by those skilled in the art as "pointing", gradually changes. This is due to the temperature increase of the laser, the complex electromechanical design and the construction of the laser. This change in pointing adversely affects the steering of the beam by the galvanometer mirrors, and sometimes even prevents drilling with the required accuracy.

[0005] As long as the laser remains on, the laser temperature and therefore the beam pointing stabilizes after a certain period of time (e.g., 5 minutes) so that the galvanometer guidance is reproducible. However, this stabilization period represents a production cycle in the drilling operation. A CO2 laser design and construction is needed that can reduce, if not completely eliminate, the pointing stabilization period. SUMMARY OF THE INVENTION

[0007] In one aspect, a laser device according to the present invention comprises an elongated gas-filled resonator unit; and an elongated radio frequency (RF) power supply unit for exciting the gas in the resonator unit. The resonator and the power supply unit are spaced apart, aligned and parallel to each other. A cooling unit comprises a plurality of elongated fins separating the resonator and the power supply unit. The fins are spaced apart and parallel to each other and extend in the length direction of the power supply and resonator unit. A plurality of fans are arranged to drive air between the spaced apart fins to cool the power supply and resonator unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate schematically preferred embodiments of the invention and, together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the invention.

[0010] Figure 1is a perspective view schematically illustrating a preferred embodiment of a CO2 waveguide-laser device according to the present invention, comprising an elongated resonator unit and an elongated power supply unit separated by an elongated cooling unit, the elongated cooling unit comprising a plurality of spaced-apart fins extending longitudinally between the resonator and the power supply unit, and a plurality of fans arranged to drive air from the center of the cooling unit through the fins to the ends.

[0011] Figure 1A Schematic description Figure 1 Longitudinal section view of a detail of a cooling unit.

[0012] Figure 1B Schematic description Figure 1 A longitudinal section isometric view of further details of the cooling unit.

[0013] Figure 1C Schematic description Figure 1 Cross-sectional views of the resonator and power supply unit details and further more details of the cooling unit.

[0014] Figure 2 is a longitudinal sectional isometric view schematically illustrating another preferred embodiment of a CO2 waveguide-laser device according to the present invention, which is similar to Figure 1 but in which the fan is arranged to drive air from the end to the center of the cooling unit through the fins of the cooling unit.

[0015] Figure 3 is an isometric view schematically illustrating another preferred embodiment of a CO2 waveguide-laser device according to the present invention, which is similar to Figure 2 An embodiment of the invention, but in which the fan is arranged to drive air through the cooling unit fins from one end of the cooling unit to the other end. DETAILED DESCRIPTION OF THE INVENTION

[0017] Turning now to the drawings, wherein like features are indicated by like reference numerals, Figure 1 , Figure 1A , Figure 1B and Figure 1C A preferred embodiment 20 of a CO2 waveguide-laser device according to the present invention is schematically described. Figure 1 Depict the complete laser. Figure 1A , 1B and 1C description Figure 1 Detail of the laser not visible in the image.

[0018] The laser 10 includes an elongated resonator unit 22 and an elongated RF power supply unit 24 for exciting the resonator unit. The resonator and power supply unit have approximately the same length and width, and are aligned parallel to each other and spaced apart by a cooling unit 26, which includes a plurality of fins 28 spaced apart from each other and parallel to each other in the width direction of the laser and extending longitudinally between the resonator and power supply unit. A plurality of fans 30 (see FIG. 1 ) on opposite sides of the cooling unit are provided. Figure 1A and 1B ) are arranged to draw air into the cooling unit and drive the air through the spaces 29 between the voids 28 to exit the cooling unit at both ends thereof.

[0019] The resonator unit 22 is a sealed housing with end plates 32 that house resonator mirrors 34, only two of which are visible in the drawing. The resonator unit 22 is preferably a folded resonator in which two mirrors terminate the resonator and others (not shown) are used to fold the resonator axis. It is noted here that only sufficient details of the resonator unit of the resonator unit 22 are described and depicted for the purpose of understanding the principles of the present invention. The details of CO2 waveguide-lasers are well known in the art. Detailed descriptions of folded resonator CO2 waveguide-lasers in various folded configurations are provided in U.S. Patent No. 6,788,722 assigned to the assignee of the present invention, and the entire disclosure of which is incorporated herein by reference.

[0020] See especially Figure 1A and 1B In the arrangement of the laser 20, the fins 28 have different lengths, being longest in the center and becoming gradually shorter towards the edges. The fins are arranged to leave ventilation spaces 31 between the fans 30 (see Figure 1A ) to receive air input from the fan. Within the ventilated space 31 are a plurality of wind deflectors or "mini fins" 27 spaced apart in the length and width directions of the cooling unit.

[0021] Without the air deflectors 27, the plenum space would not be cooled as effectively by the flowing air as the space occupied by the fins 28. The collective length of the air deflectors is selected to provide a reasonable compromise between increasing cooling efficiency in the plenum space and blocking air from entering the plenum space. Space is left between all the fins and air deflectors to accommodate a sealed power channel 36 for electrical (RF) connection between the power supply unit 24 and the resonator unit 22.

[0022] Figure 1C The preferred construction arrangement of the laser 20 of the present invention is schematically described. Here, the fins and windshield of the cold section unit 26, the housing 45, the base 46 and the wall 47, the resonator unit 22, and the base 38 and the wall 39 of the power supply unit 24 are formed from a single aluminum extrusion. The cover plate 40 and the end plate 49 ( Figure 1COnly one of them is visible) completes the housing 43 for the power supply unit. The end plate 32 is used for a complete sealed housing 45 for the resonator unit. Figure 1A and 1B The vents and wind deflectors in the cooling unit 26 shown are machined into the sides of the extrusion.The term "substrate" as applied to resonator and power units refers to the component mounting surface of the unit and is independent of the physical orientation of the unit.

[0023] Inside the housing 45 of the resonator unit is a ceramic plate 48 in which a surface of a waveguide groove 50 is machined. The plate 48 is sandwiched between the substrate 46 of the resonator unit and an electrode plate 52 electrically connected to the feedthrough 36. The groove side of the ceramic plate 48 is in contact with the substrate 46. By applying RF power to the electrode plate 52, a gas discharge is generated in the groove 50 to excite the laser-resonator.

[0024] Although the entire housing 46 is filled with laser gas, the discharge is generated only in the groove 50, because this arrangement provides that only in the groove is there an electric field sufficient to trigger and maintain the discharge. Elsewhere, the housing only provides a gas reservoir. Heat is generated due to the discharge in the groove 50. Placing the groove side of the ceramic plate 52 in contact with the substrate 46 optimizes the advantages of contact with the cooling unit 30 from the exhaust port to the side of the substrate 46.

[0025] Continue to refer Figure 1C In the power supply unit 24, the actual power supply is assembled on a printed circuit board 42 supported on a base 38 of the power supply unit. Holes 44 in the base 38 provide electrical conductors (not shown) between the power supply and the feed channel 36 of the resonator unit 22. Heat is generated in the RF power supply from the electrical impedance (not shown) of the electrical components. The power supply is placed on the base 38 of the power supply unit to optimize the heat conduction between the power supply and the cooling unit 26.

[0026] A particular advantage of central placement of the common cooling unit 26 between the resonator unit 22 and the power supply 24 is that any tendency to longitudinal bending of the laser 20 (with corresponding changes in beam pointing) is minimized, if not completely eliminated, by differential expansion between the power supply unit and the resonator unit. Any such tendency is further minimized by constructing all components from the same material (e.g., aluminum) as described above. In addition, the elongated fin configuration of the cooling unit 26 provides a high degree of longitudinal rigidity, which itself resists minimal bending tendencies that may exist due to residual differential expansion.

[0027] Figure 1 and Figure 1AThe laser shown in represents a CO2 waveguide laser with a 35 watt (W) output driven by an RF power supply with an output power of 350 W. The laser has a length of about 30 centimeters (cm) and a width of about 9 centimeters. There are twenty-seven fins 28 across the width of the cooling unit. The fins have a height of about 25 millimeters (mm), a width of about 1.7 mm, and are spaced 1.7 mm laterally.

[0028] Special References Figure 1C , the thickness T1 of the substrate 38 of the power supply unit 24 and the thickness T2 of the resonator unit 22 are selected so that the laser of the present invention is thermomechanically neutral. The term "thermomechanically neutral" means that any tendency of the laser of the present invention to bend longitudinally is minimized if not completely eliminated. In the above example, this condition can be achieved when the thickness T1 is about 6 mm and the thickness T2 is about 12 mm. In general, the thickness T1 is usually smaller than the thickness T2, which reflects that the heat generated by the power supply is more than the heat generated by the gas discharge of the laser resonator.

[0029] It is emphasized here that these above dimensions are exemplary only. Based on the description provided herein, one skilled in the art can select other dimensions for the same or different laser powers and resonator configurations without departing from the spirit and scope of the present invention. The thermal and mechanical properties of such structures can be studied using mechanical design software, such as SOLIDWORKS from Dassault Systèmes Inc. of Waltham, Massachusetts.

[0030] It should be noted here that although the present invention is described above in conjunction with a folded resonator type waveguide CO2 laser whose operating mode is guided in two mutually perpendicular transverse directions by a plurality of waveguide grooves, the principles of the present invention are equally applicable to a resonator comprising a single wide waveguide groove that guides the mode in only one transverse direction. In such a laser, the unstable resonator will be selected to guide the mode in a zigzag path in a plane perpendicular to the waveguide direction. Such lasers are generally referred to by those skilled in the art as slab CO2 lasers. One such laser is described in detail in U.S. Patent No. 8,731,015 assigned to the assignee of the present invention, the entire contents of which are incorporated herein by reference.

[0031] Figure 2 FIG. 2 is a longitudinal cross-sectional isometric view schematically illustrating another preferred embodiment of a CO2 waveguide-laser device 20A according to the present invention. The laser 20A is similar to Figure 1 and Figure 1A -C laser 20, except that a fan 30 is arranged to drive air from the end of the cooling unit through the cooling unit fins to exit laterally at the center.

[0032] Figure 3 FIG. 2 is an isometric view schematically illustrating another preferred embodiment 20B of a CO2 waveguide-laser device according to the present invention. The laser 20B is similar to Figure 2 The laser 20 of FIG. 20 is also shown, but in which the fan 30 is arranged to drive air through the cooling unit fins from one end of the cooling unit to the other end. This arrangement has the advantage that no machining operations are required in the cooling unit 26 to form the ventilation space. However, this is at the expense of a longer longitudinal temperature gradient.

[0033] In summary, the present invention has been described according to preferred and other embodiments. However, the present invention is not limited to the embodiments described and illustrated herein, but the present invention is only limited by the appended claims.

Claims

1. Laser equipment, including: an elongated gas-filled resonator unit; an elongated radio frequency (RF) power supply unit for exciting the gas in the resonator unit, the resonator and power supply unit being aligned, spaced apart and parallel to each other; The elongated cooling unit comprises a plurality of elongated fins separating the power supply and resonator units, the fins being spaced apart and parallel to each other and extending in the length direction of the power supply and resonator units, and the side edges of the fins being in direct thermal contact with the resonator unit and the power supply unit, respectively; and at least one fan arranged to flow air between the spaced apart fins to cool the power supply and resonator unit; The cooling unit further comprises a ventilation area, the ventilation area is located in a position without fins, and the ventilation area comprises a wind shield to guide air to flow out of the space between the fins.

2. The apparatus of claim 1, wherein the gas in the resonator unit is a gas mixture including carbon dioxide.

3. The apparatus of claim 1, wherein the fan is arranged so that air flows into the cooling unit at opposite ends of the cooling unit and is exhausted from near the center of the cooling unit.

4. The apparatus of claim 1 , wherein the power supply unit comprises an RF power supply mounted on a printed circuit board (PCB), and the resonator unit comprises a ceramic plate having at least one waveguide-groove in a surface thereof for guiding a lasing mode of the laser, and wherein the PCB and the ceramic plate are in thermal communication with the cooling unit.

5. The apparatus of claim 4, wherein a surface of the waveguide-groove of the ceramic plate faces the cooling unit.

6. Laser equipment, including: an elongated housing formed from a single piece of aluminum, the housing including a lower chamber holding an electrode and a laser gas, the lower chamber terminating at opposite ends of the housing by a laser mirror, the housing also including an upper chamber holding a power source for energizing the electrode, the housing also including a plurality of spaced apart machined fins extending between opposite ends of the housing and located between and directly connected to the upper and lower chambers; a pair of opposed ventilation areas located midway along the length of the shell and on side edges of the shell extending to the region of the fins, the ventilation areas including wind deflectors for directing air flow into the spaces between the fins; and At least one fan is configured to cause air to flow into the spaces between the fins, through the vent area, and out the sides of the housing near the center of the housing.

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