ARTICULATED ARM TYPE INDUSTRIAL LASER ROBOT

Abstract: An articulated arm type industrial laser robot utilizing laser robot beam passage means for bypassing a beam around a robot body, which is provided with a plurality of rotary joints having a plurality of axes of rotation which are disposed orthogonally to one another and one contractile joint on the laser beam source side, a first laser beam path changing system with a built-in laser beam reflection mirror, a plurality of rotary joints having a plurality of axes of rotation disposed orthogonally on the end side of the second arm, and a second laser beam path changing system with a built-in beam reflection mirror, for coupling and introducing the laser beam emitted from the first laser beam path changing system with and into the end portion of the robot arm on the first arm side. Accordingly, machining and assembling can be made with a desired accuracy of the beam path system as the laser beam path means. Furthermore, even during the robot operation process, the robot operation can be followed up without being affected by various errors inherent in movable portions such as the robot arm, and the laser beam can be introduced accurately into a laser beam emission portion of the wrist.

Description: The present invention relates to a multi-articulated arm type industrial robot intended for application to industrial purposes for the welding, cutting and surface-treatment of workpieces, such as metallic plates, by an emission of a laser beam introduced from a laser beam source. Various types of multi-articulated arm type industrial laser robots have been proposed and applied to practical purposes. The applicant of the present patent application has proposed, in WO 90/08621 (not a prior publication and which represents "in-house state of the art"), an improvement in such a conventional industrial laser robot, wherein a laser beam can be maintained at a high energy level. Figure 4 shows an example of such an improved industrial laser robot. As shown in Fig. 4, the improved industrial robot is a multi-articulated arm type industrial laser robot provided with at least two articulated robot arms 44 and 46 (an upper arm 44 capable of implementing a W-axis swing motion, and a lower arm 46 capable of implementing a U-axis swing motion, referred to herein as "a first robot arm" and "a second robot arm", respectively) held directly or through a swivel body 42 on a robot base 41, a robot wrist 48 held on the extremity of the articulated first robot arm 44 and the second robot arm 46 to emit a laser beam, and a laser beam passage means 50 including a hollow ball-spline shaft 54 having one end connected to the joint of the first robot arm 44 and the second robot arm 46, and a ball-spline nut combined with the ball-spline shaft 54, capable of stretching and contracting in response to the swing motions of the first and the second robot arms 44 and 46 relative to each other, the laser beam passage means 50 being extended outside the arms 44 and 46, and capable of guiding a laser beam guided thereto by a laser beam conduit 62 from outside the robot unit to the robot wrist by using the least necessary number of built-in laser beam reflecting mirrors. This improved multi-articulated industrial laser robot, however, has a problem such that, in some cases, the energy of the laser beam is not effectively used, because the laser beam passage means 50 is connected to the joints of the robot unit by optical passage connectors 58 and 60, the mode of swing motion of the laser beam passage means 50 following the motions of the first robot arm 44 and the second robot arm 46 is conducted by the help of rotary arm joint mechanisms incorporated in the joints, and it is possible that when the laser beam reaches the robot wrist 48 the laser beam is emitted along a passage at an angle to a predetermined passage due to the deflection of the axes of passages (optical axes) of the laser beam and the dislocation of the laser beam from the centers of the reflecting mirrors of the optical passage connector 58 caused by the rotational runout, tilt and dislocation of the joints attributable to various causes, including assembly errors remaining in the joints and an insufficient accuracy of rotary bearings incorporated into the joints, when reflecting the laser beam by the laser beam reflecting mirrors on the basis of the relationship between the angle of incidence and the angle of reflection. That is, although the laser beam emitting head of the robot wrist 48, in general, is provided with a condenser lens or the like, the laser beam is unable to strike the condenser lens at a correct angle of incidence and at a correct position on the condenser lens due to the deflection or dislocation of the optical passages caused by the components for directing the laser beam to the condenser lens, so that the condenser lens is unable to condense the laser beam to a spot having a predetermined diameter. Consequently, the energy of the spot of the laser beam on the workpiece cannot be increased to a level necessary for a welding, cutting or surface treatment, such as burring, which adversely affects the laser beam machining accuracy. US-A-4667081 discloses a multi-articulated arm type industrial laser robot including mutually articulated first and second robot arms, a robot wrist for emitting a laser beam, held on an end second robot arm remote from the first arm, and a laser beam passage means for routing a laser beam emitted from a laser beam source through laser beam passages arranged outside a robot unit of the laser robot; the laser beam passage means comprising a first laser beam shifting system arranged on a side of the laser beam source to include a plurality of rotary joints provided with a plurality of axes of rotation perpendicular to each other, a linear-motion joint for a telescopic linear motion, a plurality of laser beam conduit means, and internally arranged laser beam reflecting mirrors, the first laser beam shifting system being capable of routing the laser beam emitted by the laser beam source toward an end thereof; and a second laser beam shifting system arranged on a side of the extremity of the second robot arm to include a plurality of rotary joints having a plurality of axes of rotation perpendicular to each other, a plurality of laser beam conduit means, and internally arranged laser beam reflecting mirrors, the second laser beam shifting system being capable of routing the laser beam from the end of the first laser beam shifting system; and according to the present invention, such a robot is characterised in that the second laser beam shifting system is arranged to route the laser beam to a first end of the second robot arm remote from the robot wrist, from where it is, in use, routed to the robot wrist. Built as separate units separated from the robot arm system, the first and second laser beam reflecting systems can be fabricated and assembled to a desired optical accuracy, and are able to follow robot motions during an operation of the multi-articulated arm type industrial laser robot without being affected by errors in the movable components including the robot arms, thereby to route accurately the laser beam towards the laser beam emitting head of the robot wrist. In the accompanying drawings:- Fig. 1 is a perspective view of a laser beam passage means to be incorporated into a multi-articulated arm type industrial laser robot in accordance with an embodiment of the present invention; Fig. 2 is a front view, in part cross-section, of a multi-articulated industrial laser robot incorporating the laser beam passage means in accordance with the present invention; Fig. 3 is an explanatory illustration of assistance in explaining the function of a portion indicated at III in Fig. 2, and; Fig. 4 is a front view illustrating a part of the construction of a conventional multi-articulated arm type industrial laser robot. Referring first to Fig. 1, a laser beam passage means 10 embodying the present invention is intended for use on an industrial laser robot provided with a swivel body, a robot upper arm capable of implementing a W-axis swing motion, a robot forearm capable of implementing a U-axis swing motion, and a robot wrist having a laser beam emitting head and held on the extremity of the robot forearm. The laser beam passage means 10 is a movable structure which includes a first laser beam passage shifting system 20 and a second laser beam passage shifting system 30. The first laser beam passage shifting system 20 comprises a laser beam receiving unit 21 for receiving a laser beam emitted by a laser oscillator 12, i.e., a laser beam source, and traveled along a beam passage A₀ in a laser beam conduit 14, a mirror holder 22a holding a laser beam reflecting mirror 22 for shifting the laser beam in a desired direction, and a stationary cylindrical conduit unit 23 having a beam passage A₁ therein and extending downward from the mirror holder 22a. The mirror holder 22a is fixedly held on a support frame 16 fixedly installed on a fixed surface, such as the surface of the floor. A rotary cylindrical conduit 24 is joined to the lower end of the cylindrical conduit 23 for rotational motion L₁ by a rotary joint R₁ comprised of a bearing means such as an anti-friction type roller bearing or a rotary slide bearing. The laser beam travels along the beam passage A₁ through the rotary cylindrical conduit 24 and is reflected by a laser beam reflecting mirror 25 held by a mirror holder 25a at the lower end of the rotary cylindrical conduit 24 so as to travel along a beam passage A₂ through a rotary cylindrical conduit 26 and to fall on a reflecting mirror 27 held by a mirror holder 27a at a point of incidence on the reflecting mirror 27. The rotary cylindrical conduit 26 and the mirror holder 27a are capable of implementing a rotational motion L₂ relative to the mirror holder 25a. The mirror holder 25a or the mirror holder 27a is internally provided with a rotary joint R₂. The first laser beam passage shifting system 20 further includes a cylindrical conduit 28 through which the laser beam traveled along the laser beam passage A₂ and reflected by the reflecting mirror 27 travels along a laser beam passage A₃. One component 29 of the components of a precision linear motion guide means S₁ , for example, a well-known precision linear motion guide means having a ball-spline nut or a slide ball bearing, is accommodated in the free end of the cylindrical conduit 28. The base end of the second laser beam passage shifting system 30 is joined for an accurate linear motion L₃ relative to the cylindrical conduit 28 to the extremity of the cylindrical conduit 28 by the component 29 of the linear motion guide means. A cylindrical conduit 32 is provided, in one end thereof, with the other component 31 of the linear motion guide means. Thus, the laser beam reflected by the reflecting mirror 27 travels along a beam passage A₃ through the cylindrical conduit 32 and a rotary joint 33, and falls on a reflecting mirror 34 held by a reflecting mirror holder 34a. The laser beam is then reflected by the reflecting mirror 34 to travel along a beam passage A₄. A rotary joint R₃ joins the reflecting mirror holder 34a for a rotational motion L₄ relative to the circular conduit 32 to the extremity of the cylindrical conduit 32. The rotary joint R₃ internally provided with a precision rotary bearing enables the rotational motion L₄. The laser beam reflected by the reflecting mirror 34 travels along a beam passage A₄ formed through a rotary cylindrical conduit 35. The cylindrical conduit 35 has one end joined to the reflecting mirror holder 34a and the other end joined to a reflecting mirror holder 36a. A rotary joint R₄ having a rotary bearing therein is accommodated in either the reflecting mirror holder 34a or 36a, for example, in the reflecting mirror holder 34a, to permit the reflecting mirror holders 34a and 36a to rotate relative to one another for a rotational motion L₅. A reflecting mirror 36 held by the reflecting mirror holder 36a reflects the laser beam traveled along the beam passage A₄ , to make the beam travel along a beam passage A₅ through a cylindrical conduit 37. The cylindrical conduit 37 is capable of rotating relative to the reflecting mirror holder 36a. That is, the reflecting mirror holder 36a is internally provided with a rotary joint R₅ having a rotary bearing therein to enable the cylindrical conduit 37 to carry out a rotational motion L₆. The rotary cylindrical conduit 37 is provided, at an extremity thereof, with an end flange 38 to be attached to the robot unit. From the foregoing description, it will be understood that the laser beam passage means 10 in the above-mentioned embodiment has the first laser beam shifting system 20 and the second laser beam shifting system 30, and is constructed beforehand in a separate structural unit independent from the robot unit. The laser beam passage means 10 per se is a six-degree-of-freedom structural unit capable of implementing the rotational and linear motions L₁ through L₆. Namely, the construction of the laser beam passage means 10 having a plurality of degrees of freedom of motion enables the rotary joints for the rotational motions and the linear sliding joint comprising the linear guide mechanism for the linear motion to be fabricated and assembled beforehand, so that the optical passages are manufactured at a desired high accuracy. Accordingly, the laser beam passage means 10 constructed in a separate structural unit having multi-degrees of freedom of motion can be accommodated in the multi-articulated arm type industrial laser robot to arrange the laser beam passages outside the robot unit without extending the same through the joints of the robot unit in such a manner that the final beam passage is connected to an entrance of the laser beam emitting head arranged at the extremity of the robot unit. Figure 2 shows a combination of the laser beam passage means 10 of Fig. 1 and the robot unit of a multi-articulated arm type industrial laser robot, in which components, units and functions corresponding to those shown in Fig. 1 are denoted by the same reference numerals and characters. Referring to Fig. 2, the robot unit of the multi-articulated arm type industrial robot includes a base 71, a swivel body 72 mounted on the base 71 and driven by a drive motor MΘ for a swivel motion about a vertical Θ-axis, a first robot arm 74 pivotally joined by a rotary joint 73 to an offset end of the swivel body for swing motion in s vertical plane about a horizontal W-axis, a second robot arm 76 pivotally joined by a rotary joint 75 to the upper end of the first robot arm 74, a laser beam receiving unit 77 provided on the rear end of the second robot arm 76, and a robot wrist 80 having a reflecting mirror 78 therein and a laser beam emitting head 79, and attached to the front end of the second robot arm 76. The laser beam emitting head 79 is internally provided with a condenser lens 81 to emit a condensed laser beam through the condenser lens 81 to use an energy of the laser beam for laser beam machining. The end flange 38 provided at the extremity of the second laser beam shifting system 30 of the laser beam passage mean 10 is attached to the laser beam receiving unit 77 of the robot body. Thus, the laser beam emitted by the laser oscillator 12, i.e., the laser beam source, travels through the laser beam passage means 10 having the optical passages arranged outside the robot unit and enters the laser beam receiving unit 77, which is disposed at the front extremity of the arrangement of a robot movable unit including the swivel body 72 and the robot arms 74 and 76. The laser beam received by the laser beam receiving unit 77 is simply reflected by the reflecting mirror 78 so as to travel toward the laser beam emitting head 79 along the beam passage A₅. The laser beam is shifted by the laser beam emitting head 79 to travel toward the condenser lens 81. Accordingly, the laser beam guiding function of the laser beam passage means 10 is not affected by the motions of the robot unit on the rotary joints. Moreover, the laser beam passage means 10 having a plurality of degrees of freedom of linear and rotational motions L₁ through L₆ is capable of being freely moved to follow the robot motions of the robot movable unit of the robot unit on the joints. Accordingly, an accuracy of the beam passages A₁ to A₅ along which the laser beam travels depends only on an accuracy of the laser beam passage means 10, but any adverse affect of assembling errors of the joints of the robot unit as well as that of the accuracy of the rotary bearings on the functional accuracy of the beam passages A₁ through A₅ can be avoided. Referring now to Fig. 3 which is a conceptional illustration of a portion III of the laser beam receiving unit 77, the end flange 38 of the laser beam passage means 10 is fastened to a surface 77a of the laser beam receiving unit 77. Assuming that the laser beam passage mean 10 is attached to the robot unit in such a manner that the optical axis A₁ of the first laser beam shifting system 20 of the means 10 is in alignment with the vertical Θ-axis of the swivel body 72 of the robot unit as shown in Fig. 2, then the robot arms 74 and 76 of the robot unit and the surface 77a of the laser beam receiving unit 77 swing about horizontal axes, i.e., about the W-axis and the U-axis, respectively. Accordingly, when the end flange 38 of the laser beam passage means 10 is attached to the surface 77a of the laser beam receiving unit 77, and if the surface 77a should be linearly dislocated in a direction indicated by +ℓ or -ℓ (Fig. 3) and/or deflected in a direction "n" and/or a direction "m" (Fig. 3), the linear dislocation and deflection of the surface 77a can be absorbed by the movement of the laser beam passage means 10, and accordingly, the laser beam is able to travel along the optical passage A₅ and correctly strike the reflecting mirror 78 regardless of the position and orientation of the surface 77a, and the laser beam reflected by the reflecting mirror 78 is able to be condensed without errors by the condenser lens 81 of the laser beam emitting head 79. From the foregoing, it will be understood that the laser beam passage means has the laser beam passages arranged outside the robot unit of an industrial robot, and is connected to the laser beam receiving unit of the robot unit in such a manner that the motions of the joints of the motion mechanism of the robot unit do not adversely affect the accuracy of the laser beam passages along which the laser beam travels, and the laser beam receiving unit is constructed so as not to be affected by the joints of the robot unit. Therefore, the laser beam passages are able to route the laser beam from the laser beam source to the condenser lens of the laser beam emitting head at a high accuracy, if the laser beam passage means is accurately fabricated and assembled beforehand. Thus, the laser beam can travel along the beam passage in alignment with the optical axis of the condenser lens, and is able to correctly strike the center of the condenser lens. The laser beam condensed by the condenser lens is therefore emitted on an objective portion of the workpiece without entailing an energy loss due to the dislocation and variation in the diameter of the spot of the laser beam. Namely, the present invention can ensure that the laser beam machining is always maintained at a high accuracy.

Claims: A multi-articulated arm type industrial laser robot including mutually articulated first (74) and second (76) robot arms, a robot wrist (80) for emitting a laser beam, held on an end of the second robot arm remote from the first arm, and a laser beam passage means (10) for routing a laser beam emitted from a laser beam source (12) through laser beam passages arranged outside a robot unit of the laser robot; the laser beam passage means comprising a first laser beam shifting system (20) arranged on a side of the laser beam source to include a plurality of rotary joints (R₁, R₂) provided with a plurality of axes of rotation perpendicular to each other, a linear-motion joint (S₁) for a telescopic linear motion, a plurality of laser beam conduit means (23,24,26,28), and internally arranged laser beam reflecting mirrors (22,25,27), the first laser beam shifting system being capable of routing the laser beam emitted by the laser beam source toward an end thereof; and a second laser beam shifting system (30) arranged on a side of the extremity of the second robot arm to include a plurality of rotary joints (R₃,R₄,R₅) having a plurality of axes of rotation perpendicular to each other, a plurality of laser beam conduit means (32,35,37), and internally arranged laser beam reflecting mirrors (34,36), the second laser beam shifting system being capable of routing the laser beam from the end of the first laser beam shifting system; characterised in that the second laser beam shifting system is arranged to route the laser beam to a first end of the second robot arm remote from the robot wrist, from where it is, in use, routed to the robot wrist. A robot according to claim 1, wherein the first laser beam shifting system (20) comprises two rotary joints (R₁, R₂), and one telescopically movable linear-motion joint (L₃), and wherein the second laser beam shifting system (30) comprises three rotary joints (R₃,R₄,R₅) and an engaging portion (32) engaged with the telescopic linear-motion joint, whereby the laser beam passage means is provided with a six degrees of freedom of motion. A robot according to claim 2, wherein the second laser beam shifting system (30) further comprises an end flange (38) to be joined to the first end of the second robot arm (76). A robot according to claim 2 or claim 3, wherein the laser beam passage means is provided with five laser beam conduit means. A robot according to any one of the preceding claims, wherein the telescopic linear-motion joint (51) comprises a linear motion guide means.

Inventors: ITO SUSUMU FANUC MANSION HARIM, TERADA AKIHIRO FANUC MANSION H, TORII NOBUTOSHI FUYO HAITSU, ITO, SUSUMU FANUC MANSION HARIMOMI 7-204, TERADA, AKIHIRO FANUC MANSION HARIMOMI 8-207, TORII, NOBUTOSHI FUYO HAITSU 308
Applicants: FANUC LTD, FANUC LTD.
Application year: 1990
Main classification: B23K26
IPC codes: B23K26, B25J19