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EP-4493971-B1 - DEVICE FOR MOVEMENT OF AN OPTICAL UNIT, LASER PROCESS HEAD COMPRISING THE DEVICE AND EQUIPMENT COMPRISING THE LASER PROCESS HEAD

EP4493971B1EP 4493971 B1EP4493971 B1EP 4493971B1EP-4493971-B1

Inventors

  • MASOTTI, GIOVANNI
  • BOVE, ANGELO
  • Lenzi, Francesco

Dates

Publication Date
20260506
Application Date
20230313

Claims (16)

  1. A device (1) for the movement of a focusing lens (7) along an optical axis (A-A) of the focusing lens (7), the device comprising: a body (3); an optical unit (5), movable with respect to the body (3) along a translation axis (Z) and adapted to house the focusing lens (7) with the optical axis (A-A) of the focusing lens (7) parallel to the translation axis (Z) of the optical unit (5); a linear guide system parallel to the translation axis (Z); wherein the optical unit comprises a slide (11) adapted to slide along said linear guide system ;and a first magnetic actuator (23) comprising a first electromagnetic stator (25) integral with the body (3) and a first magnetic piston (27) constrained to the optical unit (5); wherein the first magnetic piston (27) is housed in a first seat (24) formed in the first electromagnetic stator (25) and movable along a first axis of motion (B-B) parallel to the translation axis (Z) of the optical unit (5); characterized by further comprising a second magnetic actuator (23), comprising a second electromagnetic stator (25) integral with the body (3) and a second magnetic piston (27) constrained to the optical unit (5); wherein the second magnetic piston (27) is housed in a second seat (24) formed in the second electromagnetic stator (25) and movable along a second axis of motion (B-B) parallel to the translation axis (Z) of the optical unit (5); wherein the first magnetic actuator (23) and the second magnetic actuator (23) are arranged symmetrically with respect to a plane of symmetry of the optical unit (5), orthogonal to a plane containing the first axis of motion (B-B) of the first magnetic actuator (23) and of the second axis of motion (B-B) of the second magnetic actuator (23); wherein the linear guide system comprises a first guide (15) and a second guide (15), parallel to one another and symmetrical with respect to the plane of symmetry; and wherein the slide (11) comprises a first shoe (17) slidingly engaged in the first guide (15) and a second shoe (17) slidingly engaged in the second guide (15).
  2. The device (1) of claim 1, wherein at least one of said first shoe (17) and second shoe (17) is connected to the optical unit (5) by an arm (19A) with notches (51, 53) adapted to allow flexional deformations of the arm in a direction connecting the centres of the first shoe (17) and the second shoe (17).
  3. The device (1) of claim 1 or 2, wherein each magnetic piston (27) has a cylindrical shape with an axis parallel to the direction of movement of the magnetic piston and with opposing magnetic poles (39N, 39S) aligned along the axis of the magnetic piston (27).
  4. The device (1) of one or more of the previous claims, wherein each electromagnetic stator (25) comprises a cylindrical wall defining a cavity, within which the respective magnetic piston is slidingly housed, and wherein the cylindrical wall (29) of each electromagnetic stator (25) is associated with at least a first electro-conductive coil (33; 35) of the electromagnetic stator (25), wherein the first electro-conductive coil (33; 35) surrounds the respective magnetic piston (27) and is coaxial thereto.
  5. The device (1) of claim 4, wherein the cylindrical wall (29) of each electromagnetic stator (25) is associated with a second electro-conductive coil (35; 33) of the electromagnetic stator (25), wherein the second electro-conductive coil (35; 33) surrounds the respective magnetic piston (27) and is coaxial thereto; wherein preferably the first electro-conductive coil (33; 35) and the second electro-conductive coil (35; 33) are connected to one another in series; and wherein preferably the first electro-conductive coil (33; 35) and the second electro-conductive coil (35; 33) of each magnetic actuator (23) are wound and can be connected to a source of current, so as to generate two opposing electromagnetic fields, which cooperate with two opposing magnetic poles (39N, 39S) of the respective magnetic piston (27).
  6. The device (1) of claim 5, wherein the electro-conductive coils (33; 35) of the first magnetic actuator (23) and of the second magnetic actuator (23) are connected to one another in series or in parallel to two poles adapted to connect to an electrical power source.
  7. The device (1) of one or more of claims 4 to 6, wherein the cylindrical wall (29) of each electromagnetic stator (25) is made of a material with high magnetic permeability and surrounds the electro-conductive coil or coils (33; 35) associated therewith.
  8. The device (1) of claim 7, wherein each magnetic piston (27) comprises a cylindrical body featuring the two opposing magnetic poles (39S, 39N), and two opposing discs (41) with high magnetic permeability associated with two opposing ends of the cylindrical body; and wherein the cylindrical wall (29) of high magnetic permeability material and the two discs (41) with high magnetic permeability form a magnetic circuit in the respective magnetic actuator (23).
  9. The device (1) of one or more of claims 4 to 8, wherein each magnetic actuator (23) comprises a system for dissipating the heat generated by the electro-conductive coils, preferably comprising one of: a thermic coupling between each electro-conductive coil and the respective cylindrical wall (29) of the electromagnetic stator (25); or a circuit for the transfer of heat from the cylindrical wall (29) of the electromagnetic stator (25) to the body (3), or both.
  10. The device (1) of one or more of the preceding claims, wherein the first magnetic piston (29) and the second magnetic piston (29) are mechanically connected to the optical unit (5) at two points located on the ends of a segment, the mid-point whereof coincides with the centre of mass of the optical unit (5).
  11. The device (1) of one or more of the previous claims, comprising a position sensor (71; 171), adapted to detect the relative position of the optical unit (5) with respect to the body (3).
  12. The device (1) of claim 11, wherein the position sensor (71; 171) comprises an electromagnetic radiation emitter (73; 173) and a linear position detector (75; 175), having a sensitive surface adapted to receive electromagnetic radiation emitted by the electromagnetic radiation emitter (73; 173); wherein the position detector (75; 175) is adapted to generate a signal that is a function of the position of a spot of electromagnetic radiation generated by the emitter (73; 173) on the sensitive surface of the position detector; wherein preferably the linear position detector is associated with a screen of the optical unit and adapted to screen external radiations; and wherein preferably the emitter (73) is integral with the optical unit (5), and wherein the position detector is integral with the body (3); and wherein the movement of the optical unit (5) along the translation axis (Z) causes a movement of the spot of electromagnetic radiation on the sensitive surface of the linear position detector (75) in a direction parallel to the direction of the translation axis (Z)
  13. The device (1) of claim 12, wherein the electromagnetic radiation emitter (173) and the linear position detector (175) are fixed with respect to one another and are integral with one of said body (3) and said optical unit (5); the position sensor comprises a cylindrical lens (177), movable integrally with the other of said body (3) and said optical unit (5), so that a relative movement between the optical unit (5) and the body (3) causes a relative movement between the cylindrical lens (177) and the linear position detector (175); wherein the cylindrical lens (177) has an axis (C-C) inclined with respect to the direction of translation (Z) of the optical unit (5); wherein the cylindrical lens has a transparent surface (177B) facing the emitter (173) and the detector (175), and an opposing reflective surface (177A), so that a beam of electromagnetic radiation emitted by the emitter (173) can pass through the cylindrical lens and can be reflected towards the linear position detector (175), forming a spot on the sensitive surface (175S) of the detector, the position of said spot being a function of the mutual position between the cylindrical lens (177) and linear position detector (175).
  14. The device (1) of one or more of the previous claims, wherein the optical unit (5) comprises a sleeve (9) adapted to house a focusing lens (7), the sleeve preferably being interchangeable; and wherein the sleeve is preferably fixed in a manner allowing it to be removed from the slide (11), for example by means of a threaded ring nut (22).
  15. A laser head comprising a laser source and a device according to one or more of the previous claims.
  16. An item of equipment comprising a laser head according to claim 15, and a system for reciprocal movement between a laser beam emitted by the laser source and a piece to be worked on using the laser beam.

Description

TECHNICAL FIELD The invention relates to a device for the movement of a focusing lens for a laser process head. BACKGROUND ART Laser sources of various kinds find application in many sectors, both medical and industrial. The laser beam generated by a source must be focused on a surface where it is necessary to concentrate the laser energy, for example to perform cutting, welding, marking or other operations. For this purpose, devices for moving a focusing lens, i.e. devices for focusing the laser beam, are provided. When the laser beam and the workpiece move rapidly relative to each other, it may be necessary to make the focusing lens perform rapid focusing movements along the optical axis thereof due to the variation in the distance between the laser head and the surface on which the laser radiation is to be focused. US 2012/087022 A1 discloses a linear motor for moving a lens. The linear motor comprises a moving magnet having a cylindrical shape and a static coil. US 9 800 128 B2 discloses a linear direct-current motor for positioning a lens comprising a lens frame, a guide rail and two symmetrically arranged actuators, each comprising a static magnet and a moving coil. US 7 859 144 B1 discloses an electromagnetic motor comprising a moving magnetic piston and two static coils with opposite winding. It would therefore be useful to have a system capable of imposing rapid and precise focusing movements on the focusing lens. SUMMARY The invention relates to a device for the movement of a focusing lens according to claim 1. To obtain a more balanced thrust, and avoid the generation of torsion moments on the optical unit, the movement device comprises a second magnetic actuator, having a second electromagnetic stator integral with the body and a second magnetic piston constrained to the optical unit. The second magnetic piston is housed in a second seat formed in the second electromagnetic stator and is movable, advantageously without contact with the second seat, along a second axis of motion parallel to the translation axis of the optical unit. To obtain a balanced thrust, without generating a moment on the optical unit, the first magnetic actuator and the second magnetic actuator are arranged symmetrically with respect to a plane of symmetry of the optical unit, orthogonal to a plane containing the first axis of motion of the first magnetic actuator and of the second axis of motion of the second magnetic actuator. The guide system comprises a first guide and a second guide, parallel to each other and symmetrical with respect to the plane of symmetry. The slide comprises a first shoe slidingly engaged in the first guide and a second shoe slidingly engaged in the second guide. In advantageous embodiments, at least one of said first shoe and second shoe is connected to the optical unit by an arm having notches adapted to allow flexural deformations of the arm along the direction of the axis joining the centre of the shoes. In some embodiments, each magnetic piston has a cylindrical configuration with an axis parallel to the direction of movement of the magnetic piston within the seat of the electromagnetic stator and with opposite magnetic poles aligned along the axis of the magnetic piston. In turn, each electromagnetic stator may comprise a cylindrical part defining the sliding seat of the respective magnetic piston. Associated with the cylindrical wall of each electromagnetic stator is at least a first electro-conductive coil surrounding the respective magnetic piston and coaxial thereto. Preferably, the cylindrical wall of each electromagnetic stator is associated with a pair of electro-conductive coils surrounding the respective magnetic piston and coaxial thereto. The two electro-conductive coils may be connected in series with each other and configured and connected to a source of current so that the same current flows in series in the two electro-conductive coils, clockwise in one of the coils and anti-clockwise in the other, and vice versa. As will become apparent from the following description, a double force generated by the linear magnetic actuator is thus obtained. Further advantageous features and embodiments of the device for the movement of a focusing lens are described below and are defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by following the description and the accompanying drawings, which illustrate an exemplifying and non-limiting embodiment of the invention. More particularly, the drawings show: Fig. 1 an isometric view of the device for the movement of an optics for a laser beam or the like in a direction parallel to the optical axis;Fig. 2 a sectional view of the device of Fig. 1 according to a plane of symmetry containing the optical axis of the focusing lens;Fig. 3 a section through one of the magnetic actuators of the movement device;Fig. 4 a front view of the movement device;Figs. 5A and 5B an enlargement of detail V of Fig