Patent Publication Number: US-2009224109-A1

Title: Articulated Robot

Description:
The present invention claims foreign priority to Japanese patent application No. 2008-053162, filed on Mar. 4, 2008, the contents of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an articulated robot, and more particularly to an articulated robot having a work machine connected to a articulation capable of rolling and a cable connected to the work machine. 
     2. Description of Related Art 
     In a process for manufacturing large amounts of automobile body, an articulated robot provided with a welding gun at the top is employed. In the welding gun, since a power of large current is required to make the spot welding, electric power is supplied from a transformer. 
     This power line is adequately thick and difficult to insert into the articulated robot, thus, the power line is disposed outside the articulated robot. 
     Also, the articulated robot has pluralities of articulations to increase a degree of freedom in the attitude of the welding gun, and particularly there is case where the top articulation has a rolling mechanism. 
     If the top articulation is rolled, a power line for the welding gun is wound on the top articulation, thus, a considerable margin is needed for the line. However, if an excessive margin is provided, a wasteful slack is produced, whereby there is a risk that the line is caught in the work machine. After all, even if the mechanical rotation angle range of the top articulation is large, the slack of the power line is decreased in operation. Therefore, the angle of roll rotation is limited, whereby the efficiency may be lower. 
     In view of this problem, Japanese Patent Unexamined Publication JP-A-2001-150382 proposes that the cable is supported by a plurality of swingable clamp members, and the attachment of the clamp members is made in the direction crossing the drive shaft direction of a robot portion, for example. 
     In the robot as described in the JP-A-2001-150382, the structure of the clamp member is complex, and the cable must be provided with a considerable slack, whereby there is still a risk that the wasteful slack is caught in the work machine. 
     SUMMARY OF THE INVENTION 
     The invention has been achieved in the light of the above-mentioned problems, and it is an object of the invention to provide an articulated robot with a simple constitution in which the cable is considerably prevented from being caught in the work machine. 
     According to the present invention, there is provided an articulated robot including: 
     a plurality of articulations comprising at least a primary articulation capable of rolling around a roll axis; 
     a work machine connected to the primary articulation; 
     a flange which is provided between the primary articulation and the work machine, and extends in a radial direction of the roll axis of the primary articulation; 
     a cable having a part connected to the work machine and another part supported on a first support portion of the primary articulation with; 
     wherein a radial dimension of at least an extending part of the flange is larger than the radial dimension of the work machine, and 
     the cable is further supported on a second support portion formed on the extending part of the flange at a portion between the work machine and the first support portion of the primary articulation. 
     Due to thus configured flange, the cable is unlikely to contact the work machine, whereby with a simple constitution, the cable can be considerably prevented from being caught in the work machine or the like. 
     In this case, the second support portion may support the cable substantially in parallel to the roll axis. Thereby, the cable can be guided in the direction away from the work machine. 
     The articulated robot may further include a cylindrical body provided between the flange and the primary articulation. A concave portion is formed on an outer circumference of the cylindrical body along with a circumferential direction of the cylindrical body. 
     Thereby, when the first articulation is rolled, the cable is wound around the concave portion, and can be prevented the cable from moving loosely. 
     Since the articulated robot according to the invention has the flange connected to the work machine and overhung in the diameter direction on the basis of the roll axis of the primary articulation, the cable is unlikely to contact the work machine, whereby with a simple constitution, the cable can be considerably prevented from being caught in the work machine or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a perspective view of an articulated robot according to an embodiment of the invention; 
         FIG. 2  is a perspective view of a top portion of the articulated robot according to this embodiment; 
         FIG. 3  is a plan view of a flange as seen from the direction of roll axis; 
         FIG. 4  is a side view of the top portion of the articulated robot according to this embodiment; 
         FIG. 5  is a side view of the top portion of the articulated robot in a state where the sixth articulation is rotated by 360° in the counterclockwise direction; 
         FIG. 6  is a plan view of the flange, as seen from the direction of roll axis, in a state where the sixth articulation is rotated by 360° in the clockwise direction; 
         FIG. 7  is a side view of the top portion of the articulated robot in a state where the welding gun is tilted by 90° plus from the state as shown in  FIG. 6 ; 
         FIG. 8  is a side view of the top portion of the articulated robot in a state where the welding gun is tilted by 90° minus from the state as shown in  FIG. 6 ; and 
         FIG. 9  is a side view of the top portion of the articulated robot in a state where the welding gun is tilted by 100° plus from the state as shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
     An articulated robot according to an exemplary embodiment of the present invention will be described below with reference to the accompanying drawings of  FIG. 1  to  FIG. 9 . 
     The articulated robot  10  according to this embodiment is a so-called industrial robot that is used to make the spot welding for the work W, and applied to, for example, a process for manufacturing a frame for automobile, as shown in  FIG. 1 . 
     The articulated robot  10  has a first articulation  14 , a second articulation  16 , a third articulation  20 , a fourth articulation  24 , a fifth articulation  28  and a sixth articulation  30  with a base board  12  on the base end, and further has a welding gun  32 , a flange  42  and a cable  44 . 
     The first articulation  14  is rotated in horizontal plane with respect to the base board  12 . The second articulation  16  is disposed near the first articulation  14 , and revolved to tilt a first arm  18 . The third articulation  20  is provided at the top of the first arm  18 , and rotated to elevate a second arm  22 . The fourth articulation  24  is provided between the second arm  22  and a third arm  26 , which are coaxial, and rolls the third arm  26  around the second arm  22 . The fifth articulation  28  is provided at the top of the third arm  26 , and rotated to swing the sixth articulation (primary articulation)  30  of the top articulation. The sixth articulation  30  is disposed near the fifth articulation  28 , and rolls the welding gun  32  that is a work machine (also called a tool or end effecter) around a roll axis J. The fourth articulation  24  and the sixth articulation  30  can be rolled by ±360°, that is, a total of 720° around the reference position. The fifth articulation  28  can be revolved by 260°. 
     In thus configured articulated robot  10  having six articulations which is independently operable, under program process of a controller, the welding gun  32  can be positioned at arbitrary position with arbitrary attitude relative to a work W. 
     The welding gun  32  is a so-called C-type gun, and includes a C-shape member (action portion)  38  having a movable electrode  34  at one side and a fixed electrode  36  at the other side, and a control portion  40  for controlling the drive and current for the movable electrode  34 , as shown in  FIG. 2 . The C-shape member  38 , the fixed electrode  36  and the movable electrode  34  are the action portion for acting on the work W. 
     The control part  40  of the welding gun  32  is connected to the sixth articulation  30 . The welding gun  32  can be removed. The welding gun  32  may be an X-shape gun or other work machines (e.g., paint spray gun). 
     A disk-like flange  42  extending in radial direction of the roll axis J is securely connected to a base end portion of the welding gun  32 . The flange  42  is made of a resin material having adequate thickness and strength and has a simple constitution. 
     The welding gun  32  is supplied with power through the cable  44 . The cable  44  has an inner electric wire (not shown) and a flexible protective tube  46  for covering the electric wire. The flexible protective tube  46  is made of a resin material or helically wounded metal material. 
     The cable  44  has one end connected to the welding gun  32 , the other end being securely supported on a first support portion  48  provided on a side surface of the third arm  26  in the articulated robot  10 . The cable  44  is connected via the first support portion  48  to a transformer  50  (see  FIG. 1 ). The cable  44  may be disposed between the first support portion  48  and the transformer  50  through an inside or outside of the articulated robot  10 . 
     The first support portion  48  is securely connected so that the cable  44  is substantially parallel to the axes of the second arm  22  and the third arm  26 . 
     A second support portion  52  for supporting a part of the cable  44  in parallel to the roll axis J is provided in a part of the peripheral edge of the flange  42 . The second support portion  52  is provided to guide the cable  44  from the front side of the flange  42  to the back side. In the second support portion  52 , the cable  44  does not need to be accurately parallel to the roll axis J, but it is enough to be fixed to be substantially parallel. Thereby, the cable  44  can easily handle the forward or backward rotation of the roll axis J, and the turnover operation in the rotational direction, whereby torsion, bend or sudden collapse can be prevented. 
     The cable  44  does not need to be firmly fixed by the second support portion  52 , but may be supported more or less tiltably. 
     The cable  44  is flexed to an extent not to produce an excessive tensile force between the second support portion  52  and a connection portion of the welding gun  32  and disposed in the almost shortest path. The cable  44  is provided with an adequate slack between the second support portion  52  and the first support portion  48 , in which a slack part rides on the flange  42  and does not hang down loosely. 
     More specifically, when the fourth articulation  24  and the sixth articulation  30  are at the respective reference angles (center position in the range of rotation angle), when viewed from a direction of the roll axis J, as shown in  FIG. 3 , the first support portion  48  is disposed on the left side of the third arm  26 , the cable  44  extends from the first support portion  48  as the point of origin to contact the left side of the upper surface of the flange  42 , and is wound about 270° clockwise on the flange  42  to lead to the second support portion  52 . The cable  44  is disposed to draw a gentle circular arc on the flange  42 , with an adequate gap from the third arm  26  or the fifth articulation  28  secured. 
     Also, the second support portion  52  is provided on the opposite side of the C-shape member  38 , when viewed from the roll axis J. 
     The flange  42  has an adequately large diameter and width, and covers almost all of the welding gun  32 , with only the C-shape member  38  of the action portion exposed (that is, the radial dimension of the C-shape member  38  is larger than the that of the flange  42 ). Also, the first support portion  48  is included in this range. Thereby, the cable  44  is likely to get on the flange  42 , and even if the cable hangs down from the periphery of the flange, the cable can be considerably prevented from contacting the welding gun  32 . 
     A cylindrical body  54  is provided between the flange  42  and the sixth articulation  30 , as shown in  FIG. 4 . An auxiliary flange  56  substantially parallel to the flange  42  is provided on the base end side of the cylindrical body  54  from the flange  42  (on the side of the sixth articulation  30 ). The auxiliary flange  56  has a smaller diameter than the flange  42 , and a slightly larger diameter than the sixth articulation  30  and the cylindrical body  54 . The auxiliary flange  56  is fixed to the welding gun  32 , together with the cylindrical body  54 , but may be attached to the fifth articulation  28  or sixth articulation  30  under the design conditions. 
     The cylindrical body  54  is connected to one flange  42  and the other auxiliary flange  56  to form a smooth arc in side view, in which the flange  42 , the auxiliary flange  56  and the cylindrical body  54  are a bobbin shape having a shallow annular concave portion. The height L of the cylindrical body  54  (i.e., distance between the flange  42  and the auxiliary flange  56 ) is slightly larger than double the diameter D of the cable  44 . That is, a concave portion is formed along with the circumferential direction on an outer circumference of the cylindrical body  54 . 
     The operation of the articulated robot  10  constituted in this way will be described below. 
     First of all, when the sixth articulation  30  is rotated by 360° in the counterclockwise direction from a state shown in  FIG. 4 , the cable  44  is wound once around the cylindrical body  54 , as shown in  FIG. 5 . At this time, since the height L is slightly larger than double the diameter D, the cable  44  is aligned in two rows around the cylindrical body  54 , and wound around the peripheral surface of the cylindrical body  54 . Accordingly, the cable  44  is not wound in large diameter loosely, and the slack of the cable  44  at the reference time (see  FIG. 4 ) is small. 
     Then, when the sixth articulation  30  is rotated by 360° in the clockwise direction from the state shown in  FIG. 4 , the cable  44  protrudes in a part (indicated by reference sign  44   a ) from the flange  42  and slightly hangs down, as shown in FIG.  6 . At this time, since the cable  44  has originally a small slack (see  FIG. 4 ) and the flange  42  has an appropriately large diameter, the length of the part  44   a  protruding from the flange  42  is short. Also, the flange  42  covers almost all of the welding gun  32 , when viewed from a direction of the roll axis J, whereby the possibility that the part  44   a  protruding from the flange  42  contacts with the welding gun  32 , or the snagging (including bite, pinching and pulling) occurs is considerably low. 
     Particularly, since the second support portion  52  is provided on the opposite side of the C-shape member  38 , the part  44   a  protruding from the flange  42  is also separated from the C-shape member  38 , whereby the possibility that the part  44   a  contacts or catches the C-shape member  38  is low, as shown in  FIG. 6 . The state as shown in  FIG. 6  is the state where the cable  44  has the largest slack. 
     Then, if the welding gun  32  is tilted upward by 90° plus (the clockwise direction in  FIGS. 7 ,  8  and  9  is defined as the plus direction, and the opposite is defined as the minus direction) from the state as shown in  FIG. 6 , a state as shown in  FIG. 7  is produced. In this state, the slack part  44   a  of the cable  44  is placed at a lower position separated from the welding gun  32  and the C-shape member  38 , in which the cable  44  does not contact or catch the welding gun  32 . 
     If the welding gun  32  is tilted downward by 90° minus from the state as shown in  FIG. 6 , a state as shown in  FIG. 8  is produced. In this case, the second support portion  52  is located above the flange  42 , and the cable  44  passes through this upper part, whereby the slack part  44   a  downward is small, and the flange  42  serves substantially as a shield between the part  44   a  and the C-shape member  38 , whereby the cable  44  can be considerably prevented from contacting or catching the welding gun  32 . 
     That is, since the second support portion  52  is provided at the opposite position of the C-shape member  38  acting on the work W in the welding gun  32 , in plan view of the flange  42  (see  FIG. 3 ), the cable  44  is always guided to the opposite position of the C-shape member  38 , so that the slack part  44   a  is unlikely to contact the C-shape member  38 . Though not shown, the same effect can be achieved when the welding gun  32  is oriented in the horizontal direction. 
     Since the second support portion  52  supports the cable  44  in parallel to the roll axis J, the cable  44  is guided in the direction away from the welding gun  32 , whereby the cable  44  is oriented to the right on the base end side from the second support portion  52  and less likely to contact with the welding gun  32  on the left side in the state as shown in  FIG. 8 , for example. A part of the cable  44  between the second support portion  52  and the welding gun  32  has almost no slack, and the snagging does not occur. 
     In  FIGS. 7 and 8 , the orientation of the welding gun  32  is changed from the state (see  FIG. 6 ) where the cable  44  has the largest slack. If the orientation of the welding gun  32  is changed from the state with the smaller slack (e.g., state as shown in  FIG. 3 ), the cable  44  is of course less likely to contact or catch the welding gun  32  than in the state as shown in  FIGS. 7 and 8 . 
     Then, if the welding gun  32  is tilted upward by about 100° plus from the state as shown in  FIG. 4 , a state as shown in  FIG. 9  is produced. In this state, the cable  44  in the cylindrical body  54  slightly slides toward the base end side (side of the sixth articulation  30 ) but contacts with the auxiliary flange  56  and is held by a part of the bobbin shape, so that there is no further movement, with the remaining slack part  44   a  being small. Accordingly, the part  44   a  can be prevented from contacting the welding gun  32  or other portions (second arm  22  and so on). 
     As described above, with the articulated robot  10  according to this embodiment, because of provision of the flange  42 , the cable  44  is less likely to contact the welding gun  32 , even if the fifth articulation  28  or sixth articulation  30  ahead of the first support portion  48  is greatly operated, whereby the cable  44  can be considerably prevented from catching the welding gun  32  with a simple constitution. 
     Accordingly, the teaching and operation making effective use of the operable range of the fifth articulation  28  or sixth articulation  30  can be performed, whereby the working efficiency is improved. 
     The cable  44  is not necessarily limited to the power cable, but may be any other flexible cable (e.g., optical fiber, fluid pipe, and a complex thereof). 
     The articulated robot according to the invention is not limited to the above embodiment, but may adopt various other constitutions without departing from the spirit or scope of the invention.