Patent Publication Number: US-2022212292-A1

Title: Machining head and three-dimensional laser processing machine using the machining head

Description:
FIELD 
     The present disclosure relates to a machining head having a multi-axis structure including two or more rotation axes, and a three-dimensional laser processing machine using the machining head. 
     BACKGROUND 
     With the development of laser technology, the performance of a laser processing machine has been dramatically improved. Accordingly, it is necessary to increase the operating speed of a machining head in order to increase the speed of laser processing. As a result, when the machining head and a workpiece collide with each other due to a mistake during a teaching operation, a programming mistake of a machining path, or the like, there is a high possibility that the device is greatly damaged. A prior art prevents damage to the entire head in the event of a collision by separating a part of the head or moving it in a direction away from an object with which the head has collided. For example, in Patent Literature 1, a buffer attached to a tip nozzle is provided with two buffer means in a perpendicular direction and a horizontal direction, and each buffer means operates depending on the direction of a collision. However, since the tip nozzle is provided with the two buffer means, there is a problem that the buffer is complex and heavy, and is not suitable for high-speed operation. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent Application Laid-open No. 2009-698 
       
    
     SUMMARY 
     Technical Problem 
     The present disclosure has been made to solve the above problem, and an object of the present disclosure is to provide a machining head capable of coping with impacts from different directions with a simple configuration of one buffer, and a three-dimensional laser processing machine using the machining head. 
     Solution to Problem 
     A machining head used for a three-dimensional laser processing machine according to the present disclosure has a multi-axis structure that rotatably supports orientation of a tip that emits a laser beam. The machining head includes a buffer installed in an arm that forms a predetermined angle with a direction in which the laser beam is emitted. The buffer includes: a first coupler that includes a first coupling surface provided near the tip; a second coupler that includes a second coupling surface facing the first coupling surface; and a coupling member to couple the first coupling surface and the second coupling surface. When a collision occurs at the tip, the first coupling surface and the second coupling surface are separated, and a separator ranging from the tip to the first coupling surface separates from a stationary body that is the arm on a side of the second coupling surface. 
     Advantageous Effects of Invention 
     According to the machining head and the three-dimensional laser processing machine using the machining head according to the present disclosure, a tip nozzle can be retreated in response to collisions from different directions by the simple configuration with one buffer, and damage to the machining head can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of a three-dimensional laser processing machine according to a first embodiment. 
         FIG. 2  is an explanatory diagram illustrating a one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment, and a state in which a buffer is installed in the machining head. 
         FIG. 3  is a diagram illustrating the buffer installed in an arm of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment. 
         FIG. 4  is an explanatory diagram illustrating an example of a retreat operation of the buffer installed in the arm immediately after a tip of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment collides with a workpiece below. 
         FIG. 5  is an explanatory diagram illustrating an example of a retreat operation of the buffer installed in the arm immediately after the tip of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment collides with a workpiece on a left side. 
         FIG. 6  is an explanatory diagram illustrating, in stages, a retreat operation of a separator in a case where the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment collides downward. 
         FIG. 7  is an explanatory diagram illustrating an example of a configuration of the buffer using permanent magnets that is installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment. 
         FIG. 8  is a block diagram illustrating a configuration of a three-dimensional laser processing machine according to a second embodiment. 
         FIG. 9  is an explanatory diagram illustrating an example of a configuration of the buffer and a collision detection sensor, the buffer being installed in the arm of a one-point oriented machining head of the three-dimensional laser processing machine according to the second embodiment. 
         FIG. 10  is an explanatory diagram illustrating an example of a configuration of the buffer and a separation detection sensor, the buffer being installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to the second embodiment. 
         FIG. 11  is an explanatory diagram illustrating the buffer using electromagnets that is installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a third embodiment. 
         FIG. 12  is an explanatory diagram illustrating the buffer using vacuum suckers that is installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a fourth embodiment. 
         FIG. 13  is an explanatory diagram illustrating the buffer using plastically deformable members and an operation of the buffer, the buffer being installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a fifth embodiment. 
         FIG. 14  is an explanatory diagram illustrating the buffer using a coil spring and an operation of the buffer, the buffer being installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a sixth embodiment. 
         FIG. 15  is an explanatory diagram illustrating the buffer using elastically deformable members and an operation of the buffer, the buffer being installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to the sixth embodiment. 
         FIG. 16  is an explanatory diagram illustrating the buffer including a wire stopper installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a seventh embodiment. 
         FIG. 17  is an explanatory diagram illustrating the buffer including a protective cover installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to eighth and ninth embodiments. 
         FIG. 18  is an explanatory diagram illustrating the buffer including a wire stopper and the protective cover installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a tenth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings. Note that in the following embodiments, similar components are denoted by the same reference numerals. 
     First Embodiment 
       FIG. 1  is a block diagram illustrating an example of a configuration of a three-dimensional laser processing machine  100  according to a first embodiment. 
       FIG. 2  is an explanatory diagram illustrating a one-point oriented machining head of the three-dimensional laser processing machine  100  according to the first embodiment, and a state in which a buffer is installed in the machining head. 
       FIG. 3  is a diagram illustrating the buffer installed in an arm of the one-point oriented machining head of the three-dimensional laser processing machine  100  according to the first embodiment. 
     The three-dimensional laser processing machine  100  according to the first embodiment illustrated in  FIG. 1  includes: a machining head  101  of a one-point oriented type that irradiates an object to be machined with a laser beam  1 ; a laser oscillator  102  that oscillates the laser beam  1  to be emitted to the machining head  101 ; a driver  103  that drives the machining head  101  and a workpiece  104 ; and a controller  105  that controls energy of the laser beam  1  and also controls the machining head  101  and the driver  103 . 
     The one-point oriented machining head is a machining head having a multi-axis structure that controls a plurality of rotation axes along an optical path through which the laser beam is transmitted to rotatably support the orientation of a tip from which the laser beam is emitted, and is installed in the three-dimensional laser processing machine to enable high-speed machining. This one-point oriented machining head has a characteristic that a machining point does not move at the time of rotating the rotation axis in the optical path through which the laser beam is sequentially reflected by a plurality of mirrors and transmitted. As illustrated in  FIG. 1 , the laser beam  1  oscillated from the laser oscillator  102  is introduced into the machining head  101  of the one-point oriented type. The machining head  101  of the one-point oriented type has a structure of five axes including: a first optical axis  11  from a tip  11   a , which is an emission port from which the laser beam  1  is emitted, to a mirror M 1 ; a second optical axis  12  from the mirror M 1  to a mirror M 2 ; a third optical axis  13  from the mirror M 2  to a mirror M 3 ; a fourth optical axis  14  from the mirror M 3  to a mirror M 4 ; and a fifth optical axis  15  from the mirror M 4  to the incident side of the laser beam. A tip nozzle  110  that emits the laser beam  1  includes a first optical axis  11 . An incident portion  150  on which the laser beam  1  is incident includes the fifth optical axis  15 . The incident portion  150  is a portion before the laser beam  1  is reflected by the mirror M 4 . 
     An arm  10  is connected to the tip nozzle  110 , and includes a first arm  120 , a second arm  130 , and a third arm  140  including the second optical axis  12 , the third optical axis  13 , and the fourth optical axis  14 , respectively. Each of the second optical axis  12 , the third optical axis  13 , and the fourth optical axis  14  forms a predetermined angle with a direction in which the laser beam  1  is emitted. That is, regarding the optical axis, three optical axes are provided between the first optical axis  11  and the fifth optical axis  15 , the three optical axes being the second optical axis  12 , the third optical axis  13 , and the fourth optical axis  14  each forming the predetermined angle with the direction in which the laser beam  1  is emitted. As for the arm  10 , the first arm  120 , the second arm  130 , and the third arm  140  each forming the predetermined angle with the direction in which the laser beam  1  is emitted are provided between the tip nozzle  110  and the incident portion  150 . As illustrated in  FIG. 2 , the laser beam  1  is reflected by the plurality of mirrors M 4 , M 3 , M 2 , and M 1  in this order along the optical path through which the laser beam  1  is transmitted, is condensed by a condensing mechanism  11   b  such as a lens provided in the tip nozzle  110  including the tip  11   a , is emitted from the tip  11   a , and reaches the workpiece  104 . 
     Next, a rotation axis and an attitude axis of the machining head  101  of the one-point oriented type will be described with reference to  FIGS. 1 and 2 . The incident portion  150  is rotatable in a direction of an arrow +α (clockwise direction in the drawing) or −α (counterclockwise direction in the drawing) around the fifth optical axis  15 . Therefore, the fifth optical axis  15  is a rotation axis that can rotate a portion of and below the mirror M 4  of the machining head  101  (that is, the fourth optical axis  14 , the third optical axis  13 , the second optical axis  12 , and the first optical axis  11 ). The second arm  130  is rotatable in a direction of an arrow +β (clockwise direction in the drawing) or −β (counterclockwise direction in the drawing) around the third optical axis  13 . Therefore, the third optical axis  13  is an attitude axis that can rotate a portion of and below the mirror M 2  (that is, the second optical axis  12  and the first optical axis  11 ). The direction in which the laser beam  1  is emitted is changed by the rotation of the attitude axis. 
     Note that the machining head of the one-point oriented type according to the first embodiment has an optical system configuration in which the laser beam is transmitted by the plurality of mirrors, but a transmission optical system using an optical fiber can also be configured using a one-point oriented machining head including an arm. When a transmission optical system using an optical fiber is used, the first optical axis  11  corresponds to a first drive axis which is an optical fiber drive axis on the emission side of the laser beam, and the second optical axis  12 , the third optical axis  13 , the fourth optical axis  14 , and the fifth optical axis  15  correspond to a second drive axis, a third drive axis, a fourth drive axis, and a fifth drive axis that are sequentially connected to the first drive axis of the optical fiber, respectively. As illustrated in  FIG. 2 , extensions of the fifth optical axis  15 , which is the rotation axis of the one-point oriented machining head, and the third optical axis  13 , which is the attitude axis thereof, are designed to always intersect at a point P, and this point P is generally the machining point. Regardless of the rotational positions of the rotation axis and the attitude axis, this machining point can always be irradiated with the laser beam. According to the three-dimensional laser processing machine having such a structure of the machining head of the one-point oriented type, the workpiece  104  can be irradiated with the laser from various directions by operating the rotation axis and the attitude axis. In general, laser irradiation is often performed such that a surface of the workpiece  104  and the direction of incidence of the laser are perpendicular to each other in accordance with the shape of the workpiece  104 . At that time, an operator needs to manually perform teaching in order to set an irradiation direction at each irradiation position of the laser. During the teaching operation and machining, the machining head and the workpiece may collide with each other due to an operation error by the operator, a difference between the actual shape of the workpiece and the drawing, or the like. 
     In the three-dimensional laser processing machine  100  according to the first embodiment, a buffer  2  is installed in order to prevent serious damage to the machining head  101  and the workpiece  104  in the event of a collision of the tip  11   a  of the machining head  101  of the one-point oriented type. As illustrated in  FIGS. 1 and 2 , the buffer  2  is installed in the arm  10 . Specifically, the buffer  2  is installed in the arm  10  between the mirror M 1  and the mirror M 2 , that is, in the first arm  120  including the second optical axis  12  which is the optical axis closest to the first optical axis  11 . Note that, in the one-point oriented machining head using the transmission optical system with an optical fiber, the arm includes a first arm including the second drive axis that forms a predetermined angle with a tip nozzle including the first drive axis on the emission side of the laser beam, a second arm including the third drive axis, and a third arm including the fourth drive axis. The third drive axis is an attitude axis capable of rotating the second drive axis and the first drive axis. Even in the one-point oriented machining head using the transmission optical system with an optical fiber, it is preferable that the buffer  2  is installed in the arm, specifically in the first arm in the arm including the second drive axis that is the drive axis closest to the first drive axis. 
     Next, the buffer  2  will be described. 
       FIG. 3  illustrates an external structure of the buffer  2  installed in the arm  10 . The buffer  2  is installed in the first arm  120  closest to the tip nozzle  110 . The buffer  2  includes a first coupler  31  and a second coupler  32 , and is provided with a coupling member  4  (not illustrated but described below) that couples the first coupler  31  and the second coupler  32 . The first coupler  31  includes a first coupling surface  3   a  and is provided near the tip nozzle  110  including the tip  11   a  that emits the laser beam  1 . The second coupler  32  includes a second coupling surface  3   b  facing the first coupling surface  3   a . That is, in the buffer  2 , the first coupler  31  including the first coupling surface  3   a  is closer to the side of the mirror M 1  on the emission side of the laser beam illustrated in  FIG. 1 , and the second coupler  32  including the second coupling surface  3   b  is closer to the side of the mirror M 2 . The coupling member  4  is provided on at least one of the first coupler  31  and the second coupler  32 , and couples two coupling surfaces  3  being the first coupling surface  3   a  and the second coupling surface  3   b . In addition, a portion from the first coupling surface  3   a  to the tip  11   a  along a direction of travel of the laser beam  1  is referred to as a separator  6   a , and a portion of the arm  10  on the side of the second coupling surface  3   b  along a direction “d” opposite to the direction of travel of the laser beam  1  is referred to as a stationary body  6   b . During normal operation, the first coupling surface  3   a  and the second coupling surface  3   b  are coupled by a coupling force f 1  by the coupling member  4 . In a case where the tip  11   a  collides with a collision force F, the first coupling surface  3   a  and the second coupling surface  3   b  are separated so that the separator  6   a  separates from the stationary body  6   b  and retreats from an object with which the tip has collided. 
     Next, a retreat operation of the buffer  2  will be described.  FIG. 4  is an explanatory diagram illustrating an example of the retreat operation of the buffer  2  installed in the arm  10  immediately after the tip  11   a  of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment collides with the workpiece  104  below.  FIG. 5  is an explanatory diagram illustrating an example of the retreat operation of the buffer  2  installed in the arm  10  immediately after the tip  11   a  of the one-point oriented machining head of the three-dimensional laser processing machine according to the first embodiment collides with the workpiece  104  on a left side. 
       FIG. 4( a )  illustrates a situation when the machining head  101  operates in the direction of an arrow  17   a , that is, in a vertically downward direction, and the tip  11   a  of the machining head  101  collides with the workpiece  104  below in the drawing with the collision force F, which occurs most frequently. The machining head  101  continues to move in the direction of the arrow  17   a  until the operation is stopped by a stop command of the controller  105 . The distance of travel of the machining head  101  in a vertical direction from  FIG. 4( a )  to  FIG. 4( b )  corresponds to “L”. In this case, as illustrated in  FIG. 4( c ) , the collision force F can be broken down into a component force f 2  of the collision force acting in a perpendicular direction  3   c  of the second coupling surface  3   b  on the side of the stationary body  6   b , and a component force f 3  of the collision force acting in a parallel direction  3   d  of the second coupling surface  3   b . As illustrated in  FIG. 4( a ) , the first coupling surface  3   a  and the second coupling surface  3   b  of the buffer  2  are coupled by the coupling force f 1  during normal operation. 
     Immediately after the collision, as illustrated in  FIG. 4( b ) , a moment acts about a coupling surface fulcrum  3   e  of the buffer  2  on a side away from the tip nozzle  110 , so that the first coupling surface  3   a  and the second coupling surface  3   b  are separated in the direction of an arrow  18   a  by the action of the component force f 2  of the collision force smaller than the coupling force f 1 . This means that the tip  11   a  retreats from the workpiece  104  in the direction of an arrow  19   a.    
       FIG. 5( a )  illustrates a situation when the machining head  101  operates in the direction of an arrow  17   b , that is, leftward in the drawing, and the tip  11   a  of the machining head  101  collides with the workpiece  104  on the left side in the drawing with the collision force F. The machining head  101  continues to move in the direction of the arrow  17   b  until the operation is stopped by a stop command of the controller  105 . The distance of travel of the machining head  101  in a horizontal direction from  FIG. 5( a )  to  FIG. 5( b )  corresponds to “L”. In this case, as illustrated in  FIG. 5( c ) , the collision force F can be broken down into the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  on the side of the stationary body  6   b , and the component force f 3  of the collision force acting in the parallel direction  3   d  of the second coupling surface  3   b . The first coupling surface  3   a  and the second coupling surface  3   b  of the buffer  2  are coupled by the coupling force f 1  during normal operation. Immediately after the collision, as illustrated in  FIG. 5( b ) , a moment acts about a coupling surface fulcrum  3   f  of the buffer  2  on a side close to the tip nozzle  110 , so that the first coupling surface  3   a  and the second coupling surface  3   b  are separated in the direction of an arrow  18   b  by the action of the component force f 2  of the collision force smaller than the coupling force f 1 . This means that the tip  11   a  retreats from the workpiece  104  in the direction of an arrow  19   b.    
     Here, since the retreat is possible in response to a smaller collision force, it is preferable to set the coupling force f 1  to be small. Meanwhile, in order to prevent the two coupling surfaces  3  from being separated at an unintended timing, the coupling force f 1  is set to a value larger than a product of multiplication of the weight of the separator  6   a  and the acceleration during the operation of the machining head  101 . In the first embodiment, the buffer  2  is installed in the first arm  120  adjacent to the tip nozzle  110  in the arm  10  with the first arm  120  having a small diameter as with the tip nozzle  110 , whereby the weight of the buffer  2  can be reduced. Furthermore, since the weight of the separator  6   a  is small, the coupling force f 1  can be set small. As a result, the two coupling surfaces  3  can be separated even in response to a smaller collision force, and the tip nozzle  110  can be retreated from the collision. 
     Also, as illustrated in  FIGS. 4 and 5 , when the machining head  101  collides, the first coupling surface  3   a  and the second coupling surface  3   b  of the buffer  2  are separated from each other by a separation distance of “L 1 ” in the perpendicular direction of the second coupling surface  3   b . In this case, the tip nozzle  110  retreats from a temporary position  110   a  (illustrated by a broken line) of the moving tip nozzle  110  to a retreat position  110   b  (illustrated by a solid line) of the tip nozzle  110  with a retreat distance of the tip  11   a  being “L 2 ”. Here, the retreat distance L 2  of the tip  11   a  is a distance in the vertical direction in  FIG. 4  and in the horizontal direction in  FIG. 5 . Note that  FIGS. 4 and 5  illustrate the examples of the operation when the collision occurs with the workpiece  104  below and on the left side, respectively. Here, depending on the direction of the collision force F, the first coupling surface  3   a  and the second coupling surface  3   b  are separated from each other with one point on the outer periphery of the second coupling surface  3   b  as a fulcrum to cause separation of the separator  6   a , or are slid away without a fulcrum to cause separation of the separator  6   a . In either case, the tip nozzle  110  can be retreated from the collision. 
       FIG. 6  illustrates the operation of the machining head  101  in three stages in the event of the collision from below as illustrated in  FIG. 4 .  FIG. 6( a )  illustrates a state in a first stage immediately before the collision,  FIG. 6( b )  illustrates a state in a second stage immediately after the collision, and  FIG. 6( c )  illustrates a state in a third stage after the collision. The machining head  101  operates in the order of the first stage to the third stage. In the second stage immediately after the collision, the first coupling surface  3   a  and the second coupling surface  3   b  are separated about the coupling surface fulcrum  3   e . In the third stage after the collision, the separator  6   a  is completely separated from the stationary body as the operation of the machining head  101  is stopped. Areas enclosed in broken lines in  FIGS. 6( b ) and 6( c )  each indicate a state of the coupling surface fulcrum  3   e . In  FIGS. 4 to 6 , the tip  11   a  of the machining head  101  is retreated from the collision by the separation of the two coupling surfaces  3 . This is an operation example where the retreat distance L 2  of the tip  11   a  is larger than the separation distance L 1  of the two coupling surfaces  3 , and is larger than the distance of travel L of the machining head  101  until the operation is stopped by the stop command of the controller. Note that even when the separation distance L 1  in the perpendicular direction of the second coupling surface  3   b  is small due to the direction in which the tip  11   a  collides, the separator  6   a  is separated from the stationary body  6   b  by the separation of the two coupling surfaces  3  of the buffer  2 , so that it is possible to prevent a collision while the machining head keeps operating at a high speed and reduce damage to the machining head. 
     Next, a description will be made of a configuration of the buffer  2  installed in the machining head  101  of the one-point oriented type of the three-dimensional laser processing machine according to the first embodiment.  FIG. 7  illustrates an explanatory diagram of an example of a configuration in which permanent magnets are used for the coupling member  4  of the buffer  2  installed in the first arm  120  of the arm  10  in the machining head  101  of the one-point oriented type of the three-dimensional laser processing machine according to the first embodiment.  FIG. 7( a )  is an explanatory diagram illustrating a structure of the buffer  2 .  FIG. 7( b )  is a diagram illustrating a cross section taken along line A-A illustrated in  FIG. 7( a ) . 
     As illustrated in  FIG. 7 , each of the first coupling surface  3   a  and the second coupling surface  3   b  is formed in a ring shape surrounding the second optical axis  12 . Permanent magnets are used for the coupling member  4 . Specifically, permanent magnets  4   a ,  4   b ,  4   c  (not illustrated), and  4   d  for coupling are provided in the first coupler  31  including the first coupling surface  3   a , and corresponding permanent magnets  4   e ,  4   f ,  4   g , and  4   h  for coupling are provided in the second coupler  32  including the second coupling surface  3   b . Note that instead of the permanent magnets, magnetic bodies  4   e ,  4   f ,  4   g , and  4   h  may be used. The two coupling surfaces  3  are coupled by the coupling force f 1  that is a magnetic force acting from the permanent magnets. The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is the magnetic force acting from the permanent magnets  4   a ,  4   b ,  4   c , and  4   d  for coupling and the corresponding permanent magnets  4   e ,  4   f ,  4   g , and  4   h  (or the magnetic bodies  4   e ,  4   f ,  4   g , and  4   h ) during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head  101 . Here, the component force f 2  of the collision force F acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Note that although the plurality of permanent magnets as the coupling member  4  illustrated in  FIG. 7  is installed along a circumferential direction of the two coupling surfaces  3 , the shape and number of the permanent magnets are not limited thereto, and, for example, permanent magnets having a ring shape along the two coupling surfaces  3  may be used. The coupling member  4  may be a combination of the permanent magnets and the permanent magnets, or a combination of the permanent magnets and the magnetic bodies. Here, when a combination of the permanent magnets and the magnetic bodies is used, the magnetic bodies can be installed in any one of the first coupler  31  and the second coupler  32 . The machining head according to the first embodiment and the three-dimensional laser processing machine using the machining head can separate a part of the machining head including the tip by the simple configuration of the buffer when the machining head collides with a workpiece or the like, and can cope with impacts from different directions. Furthermore, since the buffer is installed in the arm of the one-point oriented machining head, the buffer operation is activated even with a smaller impact by a moment of force, so that it is possible to retreat the tip nozzle and reduce damage to the machining head. 
     Second Embodiment 
       FIG. 8  is a block diagram illustrating an example of a configuration of a three-dimensional laser processing machine  200  according to a second embodiment. In the second embodiment, parts that are different from those in the first embodiment of the present disclosure will be described, and description of parts identical or corresponding to those of the first embodiment will be omitted. In a machining head  201  of the three-dimensional laser processing machine  200  according to the second embodiment, a collision detection sensor  16   a  is provided in the tip nozzle  110 , and a collision detection sensor  16   b  is provided in the buffer  2 . In  FIG. 8 , the collision detection sensors  16   a  and  16   b  make a notification to a controller  205  upon detecting an anomaly, so that the controller  205  performs control to stop the operation of the machining head  201 , block the laser beam  1 , and stop the laser irradiation until the buffer  2  is restored. Note that although both of the collision detection sensors  16   a  and  16   b  are illustrated in  FIG. 8 , only one of them may be installed. For example, only the collision detection sensor  16   b  may be installed in the buffer  2 . 
       FIG. 9( a )  is an explanatory diagram illustrating a configuration of the tip nozzle  110  in which the collision detection sensor  16   a  is installed and the buffer  2  in which the collision detection sensor  16   b  is installed in the machining head  201  of the one-point oriented type in the three-dimensional laser processing machine according to the second embodiment.  FIG. 9( b )  is a diagram illustrating a cross section taken along line A-A illustrated in  FIG. 9( a ) . Moreover,  FIG. 10  is an explanatory diagram illustrating a configuration of the buffer  2  and a separation detection sensor  16   c , the buffer being installed in the arm  10  of the one-point oriented machining head  201  of the three-dimensional laser processing machine according to the second embodiment.  FIG. 10( a )  is an explanatory diagram illustrating a structure of the buffer  2  installed in the arm  10  and the separation detection sensor  16   c .  FIG. 10( b )  is a diagram illustrating a cross section taken along line A-A illustrated in  FIG. 10( a ) . In  FIGS. 9 and 10 , the buffer  2  of the machining head  201  according to the second embodiment uses permanent magnets for the coupling member  4  as in the first embodiment, and operates in a state where the two coupling surfaces  3  are coupled by the coupling force f 1  that is a magnetic force during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. As with the first embodiment, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     First, the collision detection sensor  16   a  and the collision detection sensor  16   b  will be described. As illustrated in  FIG. 9 , the collision detection sensor  16   a  is installed in the tip  11   a . When the tip  11   a  collides, the collision detection sensor  16   a  notifies the controller  205  of the laser processing machine of the collision in order to prevent further damage, thereby causing the operation of the machining head  201  to be stopped and the laser irradiation to be stopped. A time lag always occurs before the operation of the machining head  201  is completely stopped after the collision detection sensor  16   a  detects the collision, so that the machining head  201  operates during this period of time lag. Since the machining head  201  operates at a high speed, it is desirable that the tip  11   a  of the machining head  201  be able to be retreated immediately, and that the retreat distance L 2  by which the tip  11   a  can be retreated as illustrated in  FIGS. 4 and 5  be as long as possible. Therefore, the separator  6   a  including the tip  11   a  is separated from the stationary body  6   b  by the separation of the two coupling surfaces  3  using the buffer  2  in addition to the collision detection sensor  16   a , and damage can be reduced. Note that many components such as a lens and a gas injection portion are installed in the tip nozzle  110  so that, in order to further reduce the size and weight of the separator  6   a  in the high speed operation of the machining head  201 , the collision detection sensor  16   b  may be installed in the buffer  2 . The collision detection sensor  16   b  installed on the side of the stationary body  6   b  in the buffer  2  illustrated in  FIG. 9  can similarly detect the collision of the tip  11   a , and can obtain an effect similar to that of the collision detection sensor  16   a.    
     Next, the separation detection sensor  16   c  will be described. As illustrated in  FIG. 10 , the separation detection sensor  16   c  is installed on the side of the stationary body  6   b  in the buffer  2 . The separation detection sensor  16   c  detects the separation of the two coupling surfaces  3  of the buffer  2  and detects that the two coupling surfaces  3  are coupled again after the separation operation so that the separator  6   a  is restored to the original position, thereby making a notification to the controller  205 . The controller  205  performs control to stop the operation of the machining head  201  and stop the laser irradiation before the buffer  2  is restored. Note that the separation detection sensor  16   c  may be common to the collision detection sensor  16   b  and may use the same sensor as the collision detection sensor  16   b . In this case, the separation detection sensor  16   c  detects the collision of the tip  11   a  and the separation of the two coupling surfaces  3  and makes a notification to the controller  205 , and the controller  205  performs control to stop the operation of the machining head  201 , block the laser beam  1 , and stop the laser irradiation until the buffer  2  is restored. 
     The machining head according to the second embodiment and the three-dimensional laser processing machine using the machining head can reduce damage to the machining head at the time of a collision by the simple configuration of the buffer as in the first embodiment. Furthermore, the operation of the machining head and the laser irradiation are stopped by detecting the collision and the separation of the buffer using the collision detection sensor or the separation detection sensor in combination, so that the risk of damage to the three-dimensional laser processing machine can be further reduced. 
     Third Embodiment 
       FIG. 11  illustrates an explanatory diagram of an example of a configuration in which electromagnets are used for the coupling member  4  of the buffer  2  installed in the first arm  120  of the arm in the one-point oriented machining head of the three-dimensional laser processing machine according to a third embodiment.  FIG. 11( a )  is an explanatory diagram illustrating a structure of the buffer  2 .  FIG. 11( b )  is a diagram illustrating a cross section taken along line A-A illustrated in  FIG. 11( a ) . In the third embodiment, parts that are different from those in the first embodiment of the present disclosure will be described, and description of parts identical or corresponding to those of the first embodiment will be omitted. 
     As with the configuration of the first embodiment illustrated in  FIG. 7 , in the third embodiment illustrated in  FIG. 11 , the buffer  2  is installed in the first arm  120  of the arm in the machining head of the one-point oriented type. While the permanent magnets are used for the coupling member  4  in the first embodiment, the electromagnets are used for the coupling member  4  to obtain the coupling force f 1  in the third embodiment. The two coupling surfaces  3  are coupled by the coupling force f 1  that is the electromagnetic force acting from the electromagnets. Each of the first coupling surface  3   a  and the second coupling surface  3   b  is formed in a ring shape surrounding the second optical axis  12 . Specifically, the electromagnets used for the coupling member  4  include electromagnets  5   a ,  5   b ,  5   c  (not illustrated), and  5   d  for coupling that are provided in the first coupler  31  including the first coupling surface  3   a , and corresponding electromagnets  5   e ,  5   f ,  5   g , and  5   h  for coupling that are provided in the second coupler  32  including the second coupling surface  3   b . Note that instead of the electromagnets, magnetic bodies  5   a ,  5   b ,  5   c , and  5   d  may be used. The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is the electromagnetic force acting from the electromagnets  5   a ,  5   b ,  5   c , and  5   d  (or the magnetic bodies  5   a ,  5   b ,  5   c , and  5   d ) for coupling and the corresponding electromagnets  5   e ,  5   f ,  5   g , and  5   h  for coupling during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Note that although the plurality of electromagnets as the coupling member  4  illustrated in  FIG. 11  is installed along the circumferential direction of the two coupling surfaces  3 , the shape and number of the electromagnets are not limited thereto, and, for example, electromagnets having a ring shape along the second coupling surface  3   b  may be used. The coupling member  4  may be a combination of the electromagnets and the electromagnets, or a combination of the electromagnets and the magnetic bodies. Here, when the combination of the electromagnets and the magnetic bodies is used, it is desired that the electromagnets be installed on the side of the stationary body  6   b , and the magnetic bodies be installed on the side of the separator  6   a . Moreover, when the buffer  2  of the third embodiment is used, the first embodiment may be used in combination in order for the two coupling surfaces  3  to not be separated when the power supply of the device is stopped or during a power failure. In this case, the coupling member  4  includes the permanent magnet and the electromagnet, and the two coupling surfaces  3  are coupled by the coupling force f 1  that is a total force of the magnetic force acting from the permanent magnet and the electrode force acting from the electromagnet. The permanent magnet has the magnetic force that is the minimum coupling force by which the coupling between the two coupling surfaces  3  is maintained even during a power failure. 
     Moreover, a similar effect can be obtained by a configuration in which a collision detection sensor  16   d  for detecting a collision force is installed in the tip  11   a , a notification is made to the controller of the laser processing machine when a collision of the tip  11   a  is detected, and the controller performs control to stop the current supplied to the electromagnets to cause the two coupling surfaces  3  to be separated. The collision detection sensor  16   d  can also have the function of notifying the controller of the laser processing machine of the collision. The collision detection sensor  16   d  provides the notification to the controller upon detecting the collision of the tip  11   a , so that the controller can perform control to stop the current supplied to the electromagnets to cause the two coupling surfaces  3  to be separated, and also stop the operation of the machining head and the laser irradiation. 
     The machining head according to the third embodiment and the three-dimensional laser processing machine using the machining head can reduce damage to the machining head at the time of a collision by the simple configuration of the buffer as in the first embodiment. Furthermore, by using the collision detection sensor in combination and detecting the collision, the operation of the machining head and the laser irradiation are stopped so that the risk of damage to the three-dimensional laser processing machine can be further reduced. 
     Fourth Embodiment 
       FIG. 12  is an explanatory diagram of an example of a configuration in which vacuum suckers are used for the coupling member  4  of the buffer  2  installed in the first arm  120  of the arm in the one-point oriented machining head of the three-dimensional laser processing machine according to a fourth embodiment.  FIG. 12( a )  is an explanatory diagram illustrating a structure of the buffer  2 .  FIG. 12( b )  is a diagram illustrating a cross section taken along line A-A illustrated in  FIG. 12( a ) . In the fourth embodiment, parts that are different from those in the first embodiment of the present disclosure will be described, and description of parts identical or corresponding to those of the first embodiment will be omitted. 
     As with the configuration of the first embodiment illustrated in  FIG. 7 , in the fourth embodiment illustrated in  FIG. 12 , the buffer  2  is installed in the first arm  120  of the arm in the machining head of the one-point oriented type. While the permanent magnets are used for the coupling member  4  in the first embodiment, the vacuum suckers are used for the coupling member  4  to obtain the coupling force f 1  in the fourth embodiment. The two coupling surfaces  3  are coupled by the coupling force f 1  that is the vacuum suction force acting from the vacuum suckers. The first coupling surface  3   a  and the second coupling surface  3   b  facing the first coupling surface  3   a  is each formed in a ring shape surrounding the second optical axis  12 . The coupling member  4  includes the vacuum suckers. Specifically, vacuum suckers  7   a ,  7   b ,  7   c , and  7   d  are provided in the second coupler  32  including the second coupling surface  3   b . The vacuum suckers  7   a ,  7   b ,  7   c , and  7   d  achieve a depressurized state by means (not illustrated) such as a vacuum pump to suction and couple the two coupling surfaces  3 . The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being suctioned by the vacuum suckers  7   a ,  7   b ,  7   c , and  7   d  with the coupling force f 1  during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Note that although four of the vacuum suckers used for the coupling member  4  illustrated in  FIG. 12  are installed along the circumferential direction of the second coupling surface  3   b , the shape and number of the vacuum suckers are not limited thereto, and, for example, vacuum suckers having a ring shape along the second coupling surface  3   b  may be used. Moreover, when the buffer  2  of the fourth embodiment is used, the first embodiment may be used in combination in order for the two coupling surfaces  3  to not be separated when the power supply of the device is stopped or during a power failure. In this case, the coupling member  4  includes the permanent magnet and the vacuum sucker, and the two coupling surfaces  3  are coupled by the coupling force f 1  that is a total force of the magnetic force acting from the permanent magnet and the vacuum suction force acting from the vacuum sucker. The permanent magnet has the magnetic force that is the minimum coupling force by which the coupling between the two coupling surfaces  3  is maintained even during a power failure. 
     Moreover, a similar effect can be obtained by a configuration in which a collision detection sensor  16   e  for detecting a collision force is installed in the tip  11   a , a notification is made to the controller  105  of the laser processing machine when a collision of the tip  11   a  is detected, and the controller  105  performs control to stop the current supplied to the vacuum suckers to cause the two coupling surfaces  3  to be separated. The collision detection sensor  16   e  can also have the function of notifying the controller of the laser processing machine of the collision. The collision detection sensor  16   e  provides the notification to the controller upon detecting the collision of the tip  11   a , so that the controller can perform control to stop the current supplied to the vacuum suckers to cause the two coupling surfaces  3  to be separated, and also stop the operation of the machining head and the laser irradiation. 
     The machining head according to the fourth embodiment and the three-dimensional laser processing machine using the machining head can reduce damage to the machining head at the time of a collision by the simple configuration of the buffer as in the first embodiment. Furthermore, by using the collision detection sensor in combination and detecting the collision, the operation of the machining head and the laser irradiation are stopped so that the risk of damage to the three-dimensional laser processing machine can be further reduced. 
     Fifth Embodiment 
       FIG. 13  is an explanatory diagram illustrating the buffer  2  using plastically deformable members and an operation of the buffer  2 , the buffer  2  being installed in the arm  10  of the machining head  101  of the one-point oriented type in the three-dimensional laser processing machine according to a fifth embodiment.  FIG. 13( a )  illustrates the buffer  2  during normal operation.  FIG. 13( b )  is a diagram illustrating a separated state of the buffer  2  immediately after a collision. In the fifth embodiment, parts that are different from those in the first embodiment of the present disclosure will be described, and description of parts identical or corresponding to those of the first embodiment will be omitted. 
     As with the configuration of the first embodiment illustrated in  FIG. 7 , in the fifth embodiment illustrated in  FIG. 13 , the buffer  2  is installed in the arm  10  in the machining head of the one-point oriented type. While the permanent magnets are used for the coupling member  4  in the first embodiment, the plastically deformable members are used for the coupling member  4  to obtain the coupling force f 1  in the fifth embodiment. The two coupling surfaces  3  are coupled by the coupling force f 1  that is a yield stress acting from the plastically deformable members. The coupling member  4  is a plastically deformable member with both ends fixed to corresponding ones of the first coupler  31  and the second coupler  32 , and is made of a bent wire material such as a light alloy having a low yield point. As illustrated in  FIG. 13 , plastically deformable members  8   a ,  8   b ,  8   c , and  8   d  are disposed on outer peripheries of the first coupler  31  and the second coupler  32 . The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is the yield stress by the plastically deformable members  8   a ,  8   b ,  8   c , and  8   d  during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Note that although the plurality of plastically deformable members used for the coupling member  4  illustrated in  FIG. 13  are evenly arranged along the outer peripheries of the first coupler  31  and the second coupler  32 , the shape, number, and position of arrangement of the plastically deformable members are not limited thereto. Also, as illustrated in  FIG. 13 , the collision detection sensor  16   b  is installed in the buffer  2 . In the fifth embodiment, the collision detection sensor  16   a  and the separation detection sensor  16   c  as in the second embodiment may be installed in the machining head. The machining head according to the fifth embodiment and the three-dimensional laser processing machine using the machining head can reduce damage to the machining head at the time of a collision by the simple configuration of the buffer as in the first embodiment. Furthermore, by using the collision detection sensor in combination and detecting the collision, the operation of the machining head and the laser irradiation are stopped so that the risk of damage to the three-dimensional laser processing machine can be further reduced. 
     Sixth Embodiment 
       FIG. 14  is an explanatory diagram illustrating the buffer  2  using an elastically deformable member that is a coil spring and an operation of the buffer  2 , the buffer  2  being installed in the arm  10  of the machining head of the one-point oriented type in the three-dimensional laser processing machine according to a sixth embodiment.  FIG. 14( a )  illustrates the buffer  2  during normal operation.  FIG. 14( b )  is a diagram illustrating a separated state of the buffer  2  immediately after a collision. In the sixth embodiment, parts that are different from those in the first embodiment of the present disclosure will be described, and description of parts identical or corresponding to those of the first embodiment will be omitted. 
     As with the configuration of the first embodiment illustrated in  FIG. 7 , in the sixth embodiment illustrated in  FIG. 14 , the buffer  2  is installed in the first arm  120  of the arm  10  in the machining head of the one-point oriented type. While the permanent magnets are used for the coupling member  4  in the first embodiment, the elastically deformable member that is a coil spring  9  is used for the coupling member  4  to obtain the coupling force f 1  in the sixth embodiment. The two coupling surfaces  3  are coupled by the coupling force f 1  that is an elastic force acting from the coil spring  9 . The coil spring  9  used for the coupling member  4  has both ends fixed to corresponding outer peripheries of the first coupler  31  and the second coupler  32 , and has the elastic force that presses the first coupler  31  and the second coupler  32 . The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is the elastic force by the coil spring  9  during normal operation. When the collision force F acts on the tip  11   a  of the machining head, the coil spring  9  extends and opens so that the two coupling surfaces  3  are separated. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Note that although the coil spring  9  used for the coupling member  4  illustrated in  FIG. 14  is disposed so as to be wound around the outer peripheries of the first coupler  31  and the second coupler  32 , the shape and number of the coil springs  9  are not limited thereto as long as the two coupling surfaces  3  can be coupled by the coupling force f 1  that is the elastic force.  FIG. 15  is an explanatory diagram illustrating the buffer  2  using an elastically deformable member  20  and an operation of the buffer  2  as a variation of the sixth embodiment.  FIG. 15( a )  illustrates the buffer  2  during normal operation.  FIG. 15( b )  is a diagram illustrating a separated state of the buffer  2  immediately after a collision. 
     As illustrated in  FIG. 15 , the two coupling surfaces  3  are coupled by the coupling force f 1  that is an elastic force acting from the elastically deformable member  20 . The elastically deformable member  20  having both ends fixed to corresponding ones of the first coupler  31  and the second coupler  32  and having the elastic force is used as the coupling member  4 . Specifically, elastically deformable members  20   a ,  20   b ,  20   c , and  20   d  are evenly disposed along the outer peripheries of the first coupler  31  and the second coupler  32 . The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is an elastic force by the elastically deformable members  20   a ,  20   b ,  20   c , and  20   d  during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . Also, as illustrated in  FIGS. 14 and 15 , the collision detection sensor  16   b  is installed in the buffer  2 . In the sixth embodiment, the collision detection sensor  16   a  and the separation detection sensor  16   c  as in the second embodiment may be installed in the machining head. 
     The machining head according to the sixth embodiment and the three-dimensional laser processing machine using the machining head can reduce damage to the machining head at the time of a collision by the simple configuration of the buffer as in the first embodiment. Furthermore, by using the collision detection sensor in combination and detecting the collision, the operation of the machining head and the laser irradiation are stopped so that the risk of damage to the three-dimensional laser processing machine can be further reduced. 
     Seventh Embodiment 
       FIG. 16  is a diagram illustrating the buffer  2  including a wire stopper  21  installed in the arm  10  of the one-point oriented machining head of the three-dimensional laser processing machine according to a seventh embodiment. The seventh embodiment is configured such that the machining head of the three-dimensional laser processing machine according to the first to sixth embodiments is further provided with the wire stopper  21  for reducing the risk of the separator  6   a  falling down and colliding again with the workpiece or the like when the separator  6   a  is separated. 
     As illustrated in  FIG. 16 , both ends of the wire stopper  21  having stretchability are fixed to corresponding ones of the first coupler  31  and the second coupler  32 . Note that the wire stopper  21  needs only be installed to connect the stationary body  6   b  and the separator  6   a  with the both ends fixed to corresponding ones of the stationary body  6   b  and the separator  6   a . The wire stopper  21  is flexed in a state where the two coupling surfaces  3  are coupled with the flection being pulled, whereas when the two coupling surfaces  3  are separated, the wire stopper extends to connect the stationary body  6   b  and the separator  6   a , and prevents the separator  6   a  from falling completely. Note that although  FIG. 16  illustrates one wire stopper  21  installed in the buffer  2 , the number and shape of the wire stoppers  21  are not limited thereto. 
     The machining head according to the seventh embodiment and the three-dimensional laser processing machine using the machining head have an effect similar to that of the first to sixth embodiments. Furthermore, since the wire stopper is provided in the buffer, the separator does not fall completely when separated by a collision, so that the risk of damage to the machining head and the workpiece can be reduced. In addition, when laser processing is performed again, the recovery work for coupling the two coupling surfaces can be easily performed. 
     Eighth Embodiment 
       FIG. 17  is a diagram illustrating the buffer  2  including a protective cover  22  installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to an eighth embodiment. The eighth embodiment has a configuration in which the buffer  2  is further provided with the protective cover  22  in the machining head of the three-dimensional laser processing machine according to the first to sixth embodiments. As illustrated in  FIG. 17 , the protective cover  22  is made of a cylindrical stretchable material and is, for example, a cover having a bellows structure. The protective cover  22  is installed to cover the two coupling surfaces  3  from the outer periphery of the buffer  2  so as not to expose the two coupling surfaces  3 , and can prevent foreign matter such as machining waste and dust from entering the optical path of the machining head when the two coupling surfaces  3  are separated. The protective cover  22  may also incorporate the function of the wire stopper  21  provided in the machining head according to the seventh embodiment. In this case, the protective cover  22  is installed with both ends fixed to corresponding ones of the stationary body  6   b  and the separator  6   a , and extends to cover the two coupling surfaces  3  when the two coupling surfaces  3  are separated, thereby also being able to prevent the separator  6   a  from falling completely. 
     The machining head according to the eighth embodiment and the three-dimensional laser processing machine using the machining head have an effect similar to that of the first to sixth embodiments. Furthermore, the buffer is provided with the protective cover so that even when the two coupling surfaces  3  are separated, the entry of foreign matter into the optical path of the machining head can be prevented, and a function of preventing the separator from falling can also be added to the protective cover. 
     Ninth Embodiment 
     In a ninth embodiment, a cylindrical stretchable coupling cover  23  similar to the protective cover as illustrated in  FIG. 17  is used for the coupling member  4  of the buffer  2 . As with the first to sixth embodiments, during normal operation, the two coupling surfaces  3  operate in a state of being coupled by the coupling force f 1  that is a stretching stress by the coupling member  4  using the coupling cover  23 . When the collision force F acts on the tip  11   a  of the machining head, the two coupling surfaces  3  are separated so that the separator  6   a  separates from the stationary body  6   b  and retreats from an object with which the tip has collided. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . In addition, the coupling cover  23  used for the coupling member  4  can be a protective cover having a structure that stretches in a state in which the first coupling surface  3   a  and the second coupling surface  3   b  are separated to cover the first coupling surface  3   a  and the second coupling surface  3   b . In this case, the cover also has the function of preventing entry of foreign matter into the optical path and preventing falling of the separator. That is, the function of the coupling cover and the function of the protective cover can be implemented by a single cover. 
     The machining head according to the ninth embodiment and the three-dimensional laser processing machine using the machining head have an effect similar to that of the first to sixth embodiments. Furthermore, the coupling member using the coupling cover also has an effect of preventing entry of foreign matter into the optical path and preventing falling of the separator. 
     Tenth Embodiment 
       FIG. 18  illustrates an explanatory diagram of the buffer  2  that is provided with a wire stopper  21   b  and the protective cover  22  and is installed in the arm of the one-point oriented machining head of the three-dimensional laser processing machine according to a tenth embodiment.  FIG. 18( a )  is a cross-sectional view along the second coupling surface  3   b  of the buffer  2 , and is a diagram illustrating a cross section taken along line A-A illustrated in FIG. (b).  FIG. 18( b )  is a diagram illustrating a cross section taken along line B-B illustrated in  FIG. 18( a ) . The tenth embodiment has a configuration in which the buffer  2  is further provided with the protective cover  22  and the wire stopper  21   b  in the machining head of the three-dimensional laser processing machine according to the first to sixth embodiments. 
     First, a description will be made of an example in which the permanent magnets described in the first embodiment are used for the coupling member  4  of the buffer  2  in the tenth embodiment. In the buffer  2  of the tenth embodiment, each of the first coupling surface  3   a  and the second coupling surface  3   b  is formed in a ring shape surrounding the second optical axis  12 . Permanent magnets are used for the coupling member  4 . Specifically, the first coupler  31  is provided with permanent magnets  4   i  (not illustrated),  4   j  (not illustrated), and  4   k  for coupling, and the second coupler  32  is provided with corresponding permanent magnets or magnetic bodies  4   l ,  4   m , and  4   n  for coupling. The two coupling surfaces  3  are coupled by the coupling force f 1  that is a magnetic force acting from the permanent magnets. The first coupling surface  3   a  and the second coupling surface  3   b  operate in a state of being coupled by the coupling force f 1  that is the magnetic force acting from the permanent magnets  4   i ,  4   j , and  4   k  for coupling and the corresponding permanent magnets or magnetic bodies  4   l ,  4   m , and  4   n  during normal operation. The two coupling surfaces  3  are separated when the collision force F acts on the tip  11   a  of the machining head. Here, the component force f 2  of the collision force acting in the perpendicular direction  3   c  of the second coupling surface  3   b  is smaller than the coupling force f 1 . 
     Next, the collision detection sensor  16   b  installed in the buffer  2  will be described. The collision detection sensor  16   b  is installed on the second coupling surface  3   b  of the buffer  2 . A plurality of the collision detection sensors may be installed. The collision detection sensor  16   b  makes a notification to the controller  205  as illustrated in  FIG. 8  upon detecting an anomaly, and the controller  205  performs control to stop the operation of the machining head  201  and block the laser beam  1 . The collision detection sensor  16   b  can also have a function of a separation detection sensor. As a result, the collision detection sensor  16   b  detects a separated state of the two coupling surfaces  3  and makes a notification to the controller  205 , and the controller  205  performs control to stop the laser irradiation until the buffer  2  is restored. 
     Next, the protective cover  22  and the wire stopper  21   b  installed in the buffer  2  will be described. As illustrated in  FIG. 18 , the protective cover  22  described in the eighth embodiment is provided outside the buffer  2 . The protective cover  22  is made of a cylindrical stretchable material and is, for example, a cover having a bellows structure. The protective cover  22  is installed to cover the first coupling surface  3   a  and the second coupling surface  3   b  from the outer periphery of the buffer  2  so as not to expose the first coupling surface  3   a  and the second coupling surface  3   b . The protective cover stretches to cover the buffer  2  in a state where the first coupling surface  3   a  and the second coupling surface  3   b  are separated, and prevents foreign matter such as machining waste and dust from entering the optical path of the machining head. 
     The wire stopper  21   b  made of metal is also installed outside the protective cover  22 . The wire stopper  21   b  has the same function as the wire stopper  21  described in the seventh embodiment. The wire stopper  21   b  is installed to connect the stationary body  6   b  and the separator  6   a  with both ends fixed to corresponding ones of the stationary body  6   b  and the separator  6   a.    
     As illustrated in  FIG. 18( b ) , the wire stopper  21   b  includes a wire  21   d , wire catches  21   c  attached to both ends of the wire  21   d , and a holder  21   e  with a hole larger than the wire diameter of the wire  21   d  and smaller than the outer diameter of the wire catch  21   c . The holder  21   e  is fixed to each of the stationary body  6   b  and the separator  6   a , and the wire  21   d  is held by the holder  21   e . The wire catch  21   c  is, for example, a spherical member having a diameter larger than the hole diameter of the holder  21   e . The wire  21   d  is loosened by a predetermined amount while the first coupling surface  3   a  and the second coupling surface  3   b  are coupled. The wire  21   d  of the wire stopper  21   b  extends when the separator  6   a  separates from the stationary body  6   b , but the wire catch  21   c  is caught in the hole of the holder  21   e  to prevent the separator  6   a  from falling completely. 
     Here, the wire  21   d  is held by the holder  21   e  and thus does not affect the installation of the protective cover  22 , so that the wire stopper  21   b  and the protective cover  22  can be used together. As illustrated in  FIG. 18( a ) , in the tenth embodiment, a plurality of the wire stoppers  21   b  is installed along the outer periphery of the buffer  2 . It is thus possible to cope with collisions from different directions and to prevent the separator  6   a  from falling. 
     The machining head according to the tenth embodiment and the three-dimensional laser processing machine using the machining head have an effect similar to that of the first to sixth embodiments. Furthermore, the buffer is provided with the protective cover and the wire stoppers to be able to prevent foreign matter from entering the optical path of the machining head and prevent the separator from falling completely even when the two coupling surfaces  3  are separated. The risk of damage to the machining head and the workpiece can be further reduced. 
     Note that the embodiments can be combined, modified, and/or omitted as appropriate. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  laser beam;  2  buffer;  3  two coupling surfaces;  3   a  first coupling surface;  3   b  second coupling surface;  3   c  perpendicular direction of second coupling surface;  3   d  parallel direction of second coupling surface;  3   e ,  3   f  coupling surface fulcrum;  4  coupling member;  6   a  separator;  6   b  stationary body;  9  coil spring;  10  arm; first optical axis;  11   a  tip;  12  second optical axis; third optical axis;  14  fourth optical axis;  15  fifth optical axis;  16   a ,  16   b ,  16   d ,  16   e  collision detection sensor;  16   c  separation detection sensor;  21 ,  21   b  wire stopper;  22  protective cover;  23  coupling cover;  31  first coupler;  32  second coupler;  100  three-dimensional laser processing machine;  101  machining head;  102  laser oscillator;  103  driver;  104  workpiece;  105  controller;  110  tip nozzle;  120  first arm;  130  second arm;  140  third arm;  150  incident portion;  200  three-dimensional laser processing machine;  201  machining head;  205  controller.