CA2028812A1 - Variable-pitch spot welding gun assembly for a welding robot - Google Patents
Variable-pitch spot welding gun assembly for a welding robotInfo
- Publication number
- CA2028812A1 CA2028812A1 CA002028812A CA2028812A CA2028812A1 CA 2028812 A1 CA2028812 A1 CA 2028812A1 CA 002028812 A CA002028812 A CA 002028812A CA 2028812 A CA2028812 A CA 2028812A CA 2028812 A1 CA2028812 A1 CA 2028812A1
- Authority
- CA
- Canada
- Prior art keywords
- spot welding
- welding gun
- robot
- pitch
- fixed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/12—Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/30—Features relating to electrodes
- B23K11/31—Electrode holders and actuating devices therefor
- B23K11/312—Electrode holders and actuating devices therefor for several electrodes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/10—Spot welding; Stitch welding
- B23K11/11—Spot welding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/30—Features relating to electrodes
- B23K11/31—Electrode holders and actuating devices therefor
- B23K11/314—Spot welding guns, e.g. mounted on robots
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J15/00—Gripping heads and other end effectors
Abstract
ABSTRACT
A variable pitch spot welding gun assembly for a welding robot has a fixed base (16) directly attached to the robot wrist (12) of an industrial welding robot, welding transformers (24, 26) fixed to the fixed base (16), a fixed spot welding gun (22) provided apart from the welding transformers (24, 26), a movable spot welding gun (20) provided apart from the welding transformers (24, 26) and capable of being moved relative to the fixed spot welding gun (22), to adjust a pitch between the fixed spot welding gun (22) and the movable spot welding gun (20), and secondary conductors (44a to 44e) connecting the fixed and movable spot welding guns (22, 20) respectively to the welding transformers (24, 26).
A variable pitch spot welding gun assembly for a welding robot has a fixed base (16) directly attached to the robot wrist (12) of an industrial welding robot, welding transformers (24, 26) fixed to the fixed base (16), a fixed spot welding gun (22) provided apart from the welding transformers (24, 26), a movable spot welding gun (20) provided apart from the welding transformers (24, 26) and capable of being moved relative to the fixed spot welding gun (22), to adjust a pitch between the fixed spot welding gun (22) and the movable spot welding gun (20), and secondary conductors (44a to 44e) connecting the fixed and movable spot welding guns (22, 20) respectively to the welding transformers (24, 26).
Description
~2~
DESCRIPTION
VARIABLE-PITCH SPOT WELDING GUN ASSEMBLY
FOR A WELDING ROBOT
TEC~NICAL FIELD
The present invention relates to the construction o~
a spot welding gun assembly able to be mounted on the robot wrist of a multi-articulated robot for welding (hereinafter referred to as "welding robot") for carrying out a spot-welding of a workpiece or a work, and more particularly, to a variable-pitch spot welding gun assembly for the welding robot, which assembly is provided with two spot welding guns, a sliding mechanism capable of varying the position of one of the two spot welding guns relative to the other, to thereby change a pitch therebetween, and welding transormers for supplying an electric current to the two spot welding guns, respectively, which are fixedly arranged at positions as near as possible to the robot wrist.
~.
BACKGROUND ART -Welding robots are widely used in a mass-production line for the spot-welding of, for example, auto~obile bodies, as workpi.eces. The appearance and performance o~ the robot unit of such a welding robot is described in, for example, a catalog published by Fanuc Ltd. (~ead office: Yamanashi-ken Japan): "FANUC ROBOT S Series", p.
14, Oct, 1989. A spot welding xobot incorporated into 25 such a mass-production line produces a spot-welding : -energy by transforming an electric primary voltage into a secondary voltage through an electric transformex, :
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DESCRIPTION
VARIABLE-PITCH SPOT WELDING GUN ASSEMBLY
FOR A WELDING ROBOT
TEC~NICAL FIELD
The present invention relates to the construction o~
a spot welding gun assembly able to be mounted on the robot wrist of a multi-articulated robot for welding (hereinafter referred to as "welding robot") for carrying out a spot-welding of a workpiece or a work, and more particularly, to a variable-pitch spot welding gun assembly for the welding robot, which assembly is provided with two spot welding guns, a sliding mechanism capable of varying the position of one of the two spot welding guns relative to the other, to thereby change a pitch therebetween, and welding transormers for supplying an electric current to the two spot welding guns, respectively, which are fixedly arranged at positions as near as possible to the robot wrist.
~.
BACKGROUND ART -Welding robots are widely used in a mass-production line for the spot-welding of, for example, auto~obile bodies, as workpi.eces. The appearance and performance o~ the robot unit of such a welding robot is described in, for example, a catalog published by Fanuc Ltd. (~ead office: Yamanashi-ken Japan): "FANUC ROBOT S Series", p.
14, Oct, 1989. A spot welding xobot incorporated into 25 such a mass-production line produces a spot-welding : -energy by transforming an electric primary voltage into a secondary voltage through an electric transformex, :
.
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. . ........ .. , . ~ : ~ .: .... . : . . : .. :, . . . . . . . . . . . . - .
2~2~
and applying the secondary voltage across the electrodes of the spot welding gun. Since the transformer is very h~avy, in general practice the electric transformer is installed outside the framework of the welding robot, i.e,, a robot unit, and only the spot weld.ing gun is mounted on the robot wrist in such a manner that the secondar~ voltage of the transformer is supplied to the spot welding gun through a secondary welding cable extended between the transformer and the robot unit.
Nevertheless, since the secondary welding cable is extended between the spot welding gun mounted on the robot wrist and the transformer installed apart from the robot unit, and because the welding cable used must be a heavy cable, due to a large current capacity thereof, the movement of the movable components of the robot unit, such as the robot arm or the robot wrist, is obst;ructed by the welding cable if the robot body portion or the robot arm of the robot unit becomes entwined with the welding cable.
An improvement has been made, in an attempt to solve the problems attributable to the entwinement of the movable robot components with the welding cable, in which the transformer is disposed at a particular position on the robot unit, such as near the extremity o the robot wrist. Nevertheless, there is s need for an improvement of the production efficiency of th~ welding process in the mass-production line, through the curtailment of the processing time to the least possible extent by mounting two spot welding guns on a single welding robot to form a plurality of weld spots in a single spot-welding cycle.
When the two spot welding guns each provided with an ';.~';
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2B2$8~ 2 electric transformer are mounted on the robot wrist or a part in the vicinity of the robot wrist, however, the gravitational load on the robot wrist and other movable robot components is greatly increased, and accordingly, the robot unit becomes unable to fully exhibit i~s functions and the entire robot performa:nce is restricted.
:'' DISCLOSt~RE OF THE INVENTION
Accordingly, an object of the present invention is to provide a variable-pitch spot welding gun assembly for a welding robot, which enables a full utilization of a degree or degrees of freedom of motion of the welding robot and is provided with two spot welding guns ..
supported so as to be movable toward and away from each other, to thereby curtail the time necessary for the spot welding process, and thus improve the efficiency of the spot welding process~
In the present invention, when two spot welding guns are mounted on the robot wrist of a welding robot, electric transformers or supplying electric power to the respective spot welding guns are separated from the ~-.
spot welding guns and are attached to a portion of the welding robot near the center o motion of the robot .
wrist, the two spot welding guns are mounted on the front portion of the robot wrist so that the relative pitch between the two spot welding guns can be adjusted, and the transformers are connected to the two spot ; welding guns with electric secondary cables or secondary conductors having the least possible length, respectively. .
Namely, in accordance with the present invention .
and applying the secondary voltage across the electrodes of the spot welding gun. Since the transformer is very h~avy, in general practice the electric transformer is installed outside the framework of the welding robot, i.e,, a robot unit, and only the spot weld.ing gun is mounted on the robot wrist in such a manner that the secondar~ voltage of the transformer is supplied to the spot welding gun through a secondary welding cable extended between the transformer and the robot unit.
Nevertheless, since the secondary welding cable is extended between the spot welding gun mounted on the robot wrist and the transformer installed apart from the robot unit, and because the welding cable used must be a heavy cable, due to a large current capacity thereof, the movement of the movable components of the robot unit, such as the robot arm or the robot wrist, is obst;ructed by the welding cable if the robot body portion or the robot arm of the robot unit becomes entwined with the welding cable.
An improvement has been made, in an attempt to solve the problems attributable to the entwinement of the movable robot components with the welding cable, in which the transformer is disposed at a particular position on the robot unit, such as near the extremity o the robot wrist. Nevertheless, there is s need for an improvement of the production efficiency of th~ welding process in the mass-production line, through the curtailment of the processing time to the least possible extent by mounting two spot welding guns on a single welding robot to form a plurality of weld spots in a single spot-welding cycle.
When the two spot welding guns each provided with an ';.~';
... . ., .. : . :.. :. .
2B2$8~ 2 electric transformer are mounted on the robot wrist or a part in the vicinity of the robot wrist, however, the gravitational load on the robot wrist and other movable robot components is greatly increased, and accordingly, the robot unit becomes unable to fully exhibit i~s functions and the entire robot performa:nce is restricted.
:'' DISCLOSt~RE OF THE INVENTION
Accordingly, an object of the present invention is to provide a variable-pitch spot welding gun assembly for a welding robot, which enables a full utilization of a degree or degrees of freedom of motion of the welding robot and is provided with two spot welding guns ..
supported so as to be movable toward and away from each other, to thereby curtail the time necessary for the spot welding process, and thus improve the efficiency of the spot welding process~
In the present invention, when two spot welding guns are mounted on the robot wrist of a welding robot, electric transformers or supplying electric power to the respective spot welding guns are separated from the ~-.
spot welding guns and are attached to a portion of the welding robot near the center o motion of the robot .
wrist, the two spot welding guns are mounted on the front portion of the robot wrist so that the relative pitch between the two spot welding guns can be adjusted, and the transformers are connected to the two spot ; welding guns with electric secondary cables or secondary conductors having the least possible length, respectively. .
Namely, in accordance with the present invention .
.. ,,~ . .
2 ~
there is provided a variable-pitch spot welding gun assembly for a welding robot, which comprises:
a base means directly fixed to a robot wrist of the robot;
an electrical transformer means fixedly attached to said base means for transforming an electric primary voltage into an electric secondary voltage necessary for spot-welding;
a fixed spot welding gun attached to said base means and separated from said electrical transformer means;
a movable spot welding gun movably mounted on said base means and movable relative to said fixed spot welding gun along a predetermined axis, to thereby adjust a pitch therebetween? and an electric secondary flexible conductor means e}ectrically connecting said fixed and movable spot welding guns to said electrical transformer means.
The variable-pitch spot welding gun assembly thus constructed does not obstruct the freedom of motion oE !
the movable robot components, because the two spot welding guns, i.e., the fixed spot welding gun and the movable spot welding gun, are mounted on the robot wrist, the pitch between the two spot welding guns can be adjusted according to a specified distance between spot-welding lines on a workpiece, and the spot welding guns are connected to the electric transformers mounted ;
on the robot wrist with welding cables having the least necessary length. Since the transormer for each spot welding gun is disposed near the axis of motion of the robot wrist, the moment of inertia o the robot wrist is reduced to the least possible extent, to avoid an excessive inGrease in the load on robot actions.
.: ,' ',.
2 ~
there is provided a variable-pitch spot welding gun assembly for a welding robot, which comprises:
a base means directly fixed to a robot wrist of the robot;
an electrical transformer means fixedly attached to said base means for transforming an electric primary voltage into an electric secondary voltage necessary for spot-welding;
a fixed spot welding gun attached to said base means and separated from said electrical transformer means;
a movable spot welding gun movably mounted on said base means and movable relative to said fixed spot welding gun along a predetermined axis, to thereby adjust a pitch therebetween? and an electric secondary flexible conductor means e}ectrically connecting said fixed and movable spot welding guns to said electrical transformer means.
The variable-pitch spot welding gun assembly thus constructed does not obstruct the freedom of motion oE !
the movable robot components, because the two spot welding guns, i.e., the fixed spot welding gun and the movable spot welding gun, are mounted on the robot wrist, the pitch between the two spot welding guns can be adjusted according to a specified distance between spot-welding lines on a workpiece, and the spot welding guns are connected to the electric transformers mounted ;
on the robot wrist with welding cables having the least necessary length. Since the transormer for each spot welding gun is disposed near the axis of motion of the robot wrist, the moment of inertia o the robot wrist is reduced to the least possible extent, to avoid an excessive inGrease in the load on robot actions.
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. .. , ~.. .
2~ 2 BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of ~he present inven~ion will become apparent from the ensuing description taken in conjunction with the accompanying drawings wherein:
Fig. 1 is a perspective view of a variable-pitch spot welding gun assembly for a welding robot, ln a preferred embodiment according to the present invention; and Fig. 2 is a schematic perspective view o a sliding mechanism for adjusting the distance between two spot welding guns.
BEST MODE OF CARRYING OUT THE INVENTION
Reerring to Fig. 1, a robot wrist 12 is attached to the extremity of a robot arm 10 oE a welding robot, which is a generally known multi-articulated industrial robot controlled for operation according to a predetermined motion program by a robot controller, not shown. The robot wrist 12 is free to turn about an ..
axis C and is provided at an extremity thereof with a mount, and a variable-pitch spot welding gun assembly .:, 14 provided with two spot welding guns 20 and 22 is fixedly mounted on the mount of the robot wrist 12 by generally known attaching method using a suitable attaching means including bolts and positioning pins.
The variable-pitch spot welding gun assembly 14 includes a base 16 having the shape o a box or the like and fixed to the mount o~ the robot wrist L2 by the ~::
suitable fixing means as mentioned above. Transformers 24 and 26 for supplying an electric power for welding .
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2~28~2 to the respective spot welding guns 20 and 22 are fixedly attached to the upper surface 16a of the base 16 via base plates 18. Although the transformers 24 and 26 are comparatively heavy, the moment of inertia o the transforme~s 24 and 26 during the motion of the robot wrist 12 is limited to the least possible exten~, because the transformers 24 and 26 are ~ounted on the upper surface 16a of the base 16 so that the length L
( Fig. 1 ) of the moment of inertia of the transformers 24 and 26, namely, the distance between the center of gravity of the transformers 24 and 26 and the axis c of ;,-rotation of the robot wrist, is limited to the least possible value. The transformers 24 and 26 are electrically connected to an electric power source, not shown, by electric primary cables 24a and 26a respectively, for welding to apply an electric primary voltage to the transformers 2~ and 26. The primary cables 2~a and 26a have a smaller diameter and weight than the secondary welding cables.
The output terminals 30a and 30b of the transormer 24, and the output terminals 32a and 32b of the transformer 26 are respectively connected to the two spot welding guns 20 and 22 by the secondary cables, which will be described later.
In the present embodiment, the spot welding gun 20 is a movable spot welding gun mounted on the base 16 to be laterally slid along the front surface 16b of the base 16, and the spot welding gun 22 is a ixed spot welding gun fixed to the front surface 16a of the base 16 with screw bolts or the like. The movable spot welding gun 20 is attachQd to a slider 3~ having the shape o a plate, and the fixed spot welding gun 22 is ~
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stationarily held on a fixed base plate 36 secured to the front surface 16b of the base 16. The spot welding guns 20 and 22 have identical welding units, respectively, and each welding unit comprises a pair of electrodes 40a and 40b. The electrode 40a is a movable electrode capable of being advanced and retracted by a cylinder actuator 38, and the electrode 40b is a stationary electrode disposed opposite to the movable electrode 40a. A workpiece is held between the 10 electrodes 40a and 40b for spot welding. Indicated at 42 is a rigid shunt holding the stationary electrode 40b and serving as a conductor for supplying electric welding current to the stationary electrode 40b. The electrodes 40a and 40b of the movable spot welding gun 15 20 are respectively connected to the output terminals 30a and 30b of the transformer 24 by three shunt members 44a 44b, and 44c, i.e., secondary conductors, each formed by superimposing electro-conductive and 1exible plates, such as copper plates, and having a 20 bend in the shape of the letter ~. The stationary electrode 40b is connected to the output terminal 30b by the shunt member 44c. The electrode 40b is connected to the output terminal 30a by the shunt members 44a and 44b, which are joined perpendicularly to each other~
25 Since the secondary conductor is formed of the U-shaped, electro-conductive flexible shunt members 44a to 44c, the sliding movement of the movable spot welding gun 20 and the axial movement of the movable electrode 40a caused by the cylinder actuator 38 can be smoothly and 30 readily performed.
The movable electrode 40a of the fixed spot welding gun 22 is connected to the output terminal 32a of the `` 2 ~ 2 ~ g ~
fixed txansformer 26 by a flexible and electro~
conductive shunt member 4~d having the same construction as that of the shunt members ~4a to k4c, so that the movable elec~rode 40a can be advanced and retracted with regard to the stationar~ electrode ~Ob, by the cylinder actuator 38. The stationary electrode 40b is connected to the output terminal 32b of the transformer 26 through the rigid shunt 42 by a shunt member 44e.
In the above-mentioned variable-pitch spot welding gun assembly, the movable spot welding gun 20 is individually slidable relative to the welding transformer 24, in directions indicated by a double-head arrow S, to adjust the pitch between the movable spo~- -welding gun 20 and the fixed spot welding gun 22 in compliance with a specific spot welding specification o~ a workpiece to be welded. The two spot welding guns cooperate to accomplish a highly ef~icient spot-~welding work.
A moving mechanism embodying the present invention and sliding the movable spot welding gun 20 will be described hereinafter with reference to Fig. 2.
As stated above, the box-shaped base 16 has the two welding transformers 24 an~i 26 mounted on its upper surface, and the movable spot welding gun 20 and the fixed spot welding gun 22 mounted on its front surface.
A servomotor 50 and a ball-screw shaft 52 are provided inside the base 16. The ball-screw shaft 52 has one end operatively connected to the servomotor 50 and the other end supported in a bearing 53. The servomotor 50 drives the ball-screw shaft 52 for rotation. A ball- -nut 54 is threadedly engaged with the ball-screw shaft ' ' ' . .
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52 to construct a well-known feed mechanism. As the ball-screw shaft 52 is rotated, the ball-nut 54 moves along the axis of the ball-screw shaft S2. The ball-nu~
54 stably moves along a straight guide 56 and is connected by a connecting rod 58 to the slider 34 slidable along a straight guide, not shown, disposed opposite to and in parallel to the straight guide 56, and thus the slider 34 is slid by the ball-nut 54.
Accordingly, the movable spot welding gun 20 attached to the slider 34 is moved laterally together with the slider 34, in directions indicated by the double-head arrow S, to adjust the pitch between the movable spot welding gun 20 and the fixed spot welding gun 22 by -controlling the angle of rotation of the motor 50.
As apparent from the foregoing description, since in the spot welding gun assembly 14 in accordance with the present invention the two spot welding guns 20 and 22 are supported so that the pitch between the spot welding guns 20 and 22 is adjustable, and the weldins transformers 24 and 26 are mounted on the extremity of the robot wrist, the spot welding gun assembly 14 is capable of carrying out highly e~ficient spot w21ding -work in an automobile mass-production line or the like, :
and of automatically changing the spot welding spacing according to the change of spot welding specifications for the work. Since the welding transformers are disposed near the center of motion of the robot wrist, the moment acting on the robot can be reduced to the least possible extent, and thus sufficiently ~ree motions of the robot wrist can be secured. Further since the spot welding guns are connected to the transformers with short, flexlble conductive shunts to the " .
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corresponding transformers, restrictions on ~he operation of the conventional welding robot attributable to the secondary cables are eliminated.
Furthermore, according to the present invention, the two spot welding guns, i.e., the movable spot gun welding gun and the fixed spot welding gun, integrated into the spot welding robot significantly improve the working efficiency and performance of ~he spot welding robot, and the arrangement of the electric transformers at the extremity of the robot wrist eliminates problems attributable to the obstruction of the free motion of the robot by the secondary cables. Note, the shunt member employed as a secondary cable in the foregoing embodiment is merely an example; the present invention may employ a flexible, stretchable cable structure, `
such as a structure consistin~ of a stretchable, resilient cable holder and a cable held on the cable holder, for the same unction and utility.
i' -. .: .
- ~ O- .. , 2B28~ ~ 2 LIST OF R~F~RENCE CHARACTERS
Robot arm 12 Robot wrist 14 Spot welding gun assembly 16 Base 18 Base plate Movable spot welding gun 22 Fixed spot welding gun :~
24, 26 Welding transformsrs 24a, 26a Primary cables 3Qa, 30b Output terminals 32a, 32b Output terminals 34 Slider 36 Fixed base plate 38 Cylinder actuator 40a Movable electrode 40b Stationary electrode 42 Shunt 44a, 44b, 44c Shunt members 44d Flexible conductive shunt member 44e Shunt 50 ` Servomotor r 52 Ball-screw shaft 53 Bearing 54 Ball-nut 56 Straight guide 58 Connecting rod '.' ' - .
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.
.
... . .. .
. .. , ~.. .
2~ 2 BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of ~he present inven~ion will become apparent from the ensuing description taken in conjunction with the accompanying drawings wherein:
Fig. 1 is a perspective view of a variable-pitch spot welding gun assembly for a welding robot, ln a preferred embodiment according to the present invention; and Fig. 2 is a schematic perspective view o a sliding mechanism for adjusting the distance between two spot welding guns.
BEST MODE OF CARRYING OUT THE INVENTION
Reerring to Fig. 1, a robot wrist 12 is attached to the extremity of a robot arm 10 oE a welding robot, which is a generally known multi-articulated industrial robot controlled for operation according to a predetermined motion program by a robot controller, not shown. The robot wrist 12 is free to turn about an ..
axis C and is provided at an extremity thereof with a mount, and a variable-pitch spot welding gun assembly .:, 14 provided with two spot welding guns 20 and 22 is fixedly mounted on the mount of the robot wrist 12 by generally known attaching method using a suitable attaching means including bolts and positioning pins.
The variable-pitch spot welding gun assembly 14 includes a base 16 having the shape o a box or the like and fixed to the mount o~ the robot wrist L2 by the ~::
suitable fixing means as mentioned above. Transformers 24 and 26 for supplying an electric power for welding .
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2~28~2 to the respective spot welding guns 20 and 22 are fixedly attached to the upper surface 16a of the base 16 via base plates 18. Although the transformers 24 and 26 are comparatively heavy, the moment of inertia o the transforme~s 24 and 26 during the motion of the robot wrist 12 is limited to the least possible exten~, because the transformers 24 and 26 are ~ounted on the upper surface 16a of the base 16 so that the length L
( Fig. 1 ) of the moment of inertia of the transformers 24 and 26, namely, the distance between the center of gravity of the transformers 24 and 26 and the axis c of ;,-rotation of the robot wrist, is limited to the least possible value. The transformers 24 and 26 are electrically connected to an electric power source, not shown, by electric primary cables 24a and 26a respectively, for welding to apply an electric primary voltage to the transformers 2~ and 26. The primary cables 2~a and 26a have a smaller diameter and weight than the secondary welding cables.
The output terminals 30a and 30b of the transormer 24, and the output terminals 32a and 32b of the transformer 26 are respectively connected to the two spot welding guns 20 and 22 by the secondary cables, which will be described later.
In the present embodiment, the spot welding gun 20 is a movable spot welding gun mounted on the base 16 to be laterally slid along the front surface 16b of the base 16, and the spot welding gun 22 is a ixed spot welding gun fixed to the front surface 16a of the base 16 with screw bolts or the like. The movable spot welding gun 20 is attachQd to a slider 3~ having the shape o a plate, and the fixed spot welding gun 22 is ~
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.
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stationarily held on a fixed base plate 36 secured to the front surface 16b of the base 16. The spot welding guns 20 and 22 have identical welding units, respectively, and each welding unit comprises a pair of electrodes 40a and 40b. The electrode 40a is a movable electrode capable of being advanced and retracted by a cylinder actuator 38, and the electrode 40b is a stationary electrode disposed opposite to the movable electrode 40a. A workpiece is held between the 10 electrodes 40a and 40b for spot welding. Indicated at 42 is a rigid shunt holding the stationary electrode 40b and serving as a conductor for supplying electric welding current to the stationary electrode 40b. The electrodes 40a and 40b of the movable spot welding gun 15 20 are respectively connected to the output terminals 30a and 30b of the transformer 24 by three shunt members 44a 44b, and 44c, i.e., secondary conductors, each formed by superimposing electro-conductive and 1exible plates, such as copper plates, and having a 20 bend in the shape of the letter ~. The stationary electrode 40b is connected to the output terminal 30b by the shunt member 44c. The electrode 40b is connected to the output terminal 30a by the shunt members 44a and 44b, which are joined perpendicularly to each other~
25 Since the secondary conductor is formed of the U-shaped, electro-conductive flexible shunt members 44a to 44c, the sliding movement of the movable spot welding gun 20 and the axial movement of the movable electrode 40a caused by the cylinder actuator 38 can be smoothly and 30 readily performed.
The movable electrode 40a of the fixed spot welding gun 22 is connected to the output terminal 32a of the `` 2 ~ 2 ~ g ~
fixed txansformer 26 by a flexible and electro~
conductive shunt member 4~d having the same construction as that of the shunt members ~4a to k4c, so that the movable elec~rode 40a can be advanced and retracted with regard to the stationar~ electrode ~Ob, by the cylinder actuator 38. The stationary electrode 40b is connected to the output terminal 32b of the transformer 26 through the rigid shunt 42 by a shunt member 44e.
In the above-mentioned variable-pitch spot welding gun assembly, the movable spot welding gun 20 is individually slidable relative to the welding transformer 24, in directions indicated by a double-head arrow S, to adjust the pitch between the movable spo~- -welding gun 20 and the fixed spot welding gun 22 in compliance with a specific spot welding specification o~ a workpiece to be welded. The two spot welding guns cooperate to accomplish a highly ef~icient spot-~welding work.
A moving mechanism embodying the present invention and sliding the movable spot welding gun 20 will be described hereinafter with reference to Fig. 2.
As stated above, the box-shaped base 16 has the two welding transformers 24 an~i 26 mounted on its upper surface, and the movable spot welding gun 20 and the fixed spot welding gun 22 mounted on its front surface.
A servomotor 50 and a ball-screw shaft 52 are provided inside the base 16. The ball-screw shaft 52 has one end operatively connected to the servomotor 50 and the other end supported in a bearing 53. The servomotor 50 drives the ball-screw shaft 52 for rotation. A ball- -nut 54 is threadedly engaged with the ball-screw shaft ' ' ' . .
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2~28~ ~
52 to construct a well-known feed mechanism. As the ball-screw shaft 52 is rotated, the ball-nut 54 moves along the axis of the ball-screw shaft S2. The ball-nu~
54 stably moves along a straight guide 56 and is connected by a connecting rod 58 to the slider 34 slidable along a straight guide, not shown, disposed opposite to and in parallel to the straight guide 56, and thus the slider 34 is slid by the ball-nut 54.
Accordingly, the movable spot welding gun 20 attached to the slider 34 is moved laterally together with the slider 34, in directions indicated by the double-head arrow S, to adjust the pitch between the movable spot welding gun 20 and the fixed spot welding gun 22 by -controlling the angle of rotation of the motor 50.
As apparent from the foregoing description, since in the spot welding gun assembly 14 in accordance with the present invention the two spot welding guns 20 and 22 are supported so that the pitch between the spot welding guns 20 and 22 is adjustable, and the weldins transformers 24 and 26 are mounted on the extremity of the robot wrist, the spot welding gun assembly 14 is capable of carrying out highly e~ficient spot w21ding -work in an automobile mass-production line or the like, :
and of automatically changing the spot welding spacing according to the change of spot welding specifications for the work. Since the welding transformers are disposed near the center of motion of the robot wrist, the moment acting on the robot can be reduced to the least possible extent, and thus sufficiently ~ree motions of the robot wrist can be secured. Further since the spot welding guns are connected to the transformers with short, flexlble conductive shunts to the " .
,' ~ ":
, .
"' 2 ~
corresponding transformers, restrictions on ~he operation of the conventional welding robot attributable to the secondary cables are eliminated.
Furthermore, according to the present invention, the two spot welding guns, i.e., the movable spot gun welding gun and the fixed spot welding gun, integrated into the spot welding robot significantly improve the working efficiency and performance of ~he spot welding robot, and the arrangement of the electric transformers at the extremity of the robot wrist eliminates problems attributable to the obstruction of the free motion of the robot by the secondary cables. Note, the shunt member employed as a secondary cable in the foregoing embodiment is merely an example; the present invention may employ a flexible, stretchable cable structure, `
such as a structure consistin~ of a stretchable, resilient cable holder and a cable held on the cable holder, for the same unction and utility.
i' -. .: .
- ~ O- .. , 2B28~ ~ 2 LIST OF R~F~RENCE CHARACTERS
Robot arm 12 Robot wrist 14 Spot welding gun assembly 16 Base 18 Base plate Movable spot welding gun 22 Fixed spot welding gun :~
24, 26 Welding transformsrs 24a, 26a Primary cables 3Qa, 30b Output terminals 32a, 32b Output terminals 34 Slider 36 Fixed base plate 38 Cylinder actuator 40a Movable electrode 40b Stationary electrode 42 Shunt 44a, 44b, 44c Shunt members 44d Flexible conductive shunt member 44e Shunt 50 ` Servomotor r 52 Ball-screw shaft 53 Bearing 54 Ball-nut 56 Straight guide 58 Connecting rod '.' ' - .
, ~ , ':
.
.
Claims (6)
1. A variable-pitch spot welding gun assembly for a welding robot, comprising:
a base means directly fixed to a robot wrist of the robot;
an electrical transformer means fixedly attached to said base means for transforming an electric primary voltage into an electric secondary voltage necessary for spot-welding;
a fixed spot welding gun attached to said base means and separated form said electrical transformer means;
a movable spot welding gun movably mounted on said base means and movable relative to said fixed spot welding gun along a predetermined axis to thereby adjust a pitch therebetween; and an electric secondary flexible conductor means electrically connecting said fixed and movable spot welding guns to said electrical transformer means.
a base means directly fixed to a robot wrist of the robot;
an electrical transformer means fixedly attached to said base means for transforming an electric primary voltage into an electric secondary voltage necessary for spot-welding;
a fixed spot welding gun attached to said base means and separated form said electrical transformer means;
a movable spot welding gun movably mounted on said base means and movable relative to said fixed spot welding gun along a predetermined axis to thereby adjust a pitch therebetween; and an electric secondary flexible conductor means electrically connecting said fixed and movable spot welding guns to said electrical transformer means.
2. A variable-pitch spot welding gun assembly according to claim 1, wherein said base means is internally provided with a shifting means for moving said movable spot welding gun relative to said fixed spot welding gun to thereby adjust the pitch between said fixed and movable spot welding guns.
3. A variable-pitch spot welding gun assembly according to claim 2, wherein said base means comprises a base body, and wherein said shifting means comprises a ball-screw shaft rotatably supported inside said base body, a ball-nut threadedly engaged with said ball-screw shaft, a slider connected to said ball-nut and having a mounting surface to which said movable spot welding gun is attached, and a motor for rotationally driving said ball-screw shaft.
4. A variable-pitch spot welding gun assembly according to claim 3, wherein said base body of said base means is provided with a mounting surface for holding said electric transformer means thereon at a position as near as possible to an axis of motion of said robot wrist.
5. A variable-pitch spot welding gun assembly according to claim 1, wherein said electric transformer means comprises first and second electric transformers fixedly disposed with a fixed space therebetween along said predetermined axis, said first electric transformer being connected to said fixed spot welding gun, and said second electric transformer being connected to said movable spot welding gun.
6, A variable-pitch spot welding gun assembly according to claim 1, wherein said flexible secondary conductor means comprises a plurality of U-shaped electrical shunt members each formed by superimposing conductive plates capable of flexing at least in directions of movement of said movable spot welding gun.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1065975A JP2580029B2 (en) | 1989-03-20 | 1989-03-20 | Variable-pitch spot welding gun device for welding robot |
| JP1-65975 | 1989-03-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2028812A1 true CA2028812A1 (en) | 1990-09-21 |
Family
ID=13302511
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002028812A Abandoned CA2028812A1 (en) | 1989-03-20 | 1990-03-19 | Variable-pitch spot welding gun assembly for a welding robot |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5111019A (en) |
| EP (1) | EP0418395B1 (en) |
| JP (1) | JP2580029B2 (en) |
| KR (1) | KR930004998B1 (en) |
| CA (1) | CA2028812A1 (en) |
| DE (1) | DE69009130T2 (en) |
| WO (1) | WO1990011160A1 (en) |
Families Citing this family (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0825029B2 (en) * | 1991-03-22 | 1996-03-13 | 本田技研工業株式会社 | X type welding gun device |
| JPH0528569U (en) * | 1991-09-24 | 1993-04-16 | 三菱自動車工業株式会社 | Spot welder |
| CN1065163C (en) * | 1992-03-10 | 2001-05-02 | 李崇蓉 | Hanging spot-welder with transformer |
| CN1067314C (en) * | 1996-08-20 | 2001-06-20 | 李崇蓉 | Method for connecting transformer secondary output of suspended mash welder |
| JP2943731B2 (en) * | 1996-10-28 | 1999-08-30 | トヨタ自動車株式会社 | Welding equipment |
| WO2001036141A1 (en) * | 1999-11-19 | 2001-05-25 | Dct, Inc. | Multi-arm weld gun |
| US20040045940A1 (en) * | 2002-09-05 | 2004-03-11 | Angel Jeffrey R. | Pinch weld gun with curvilinear shunt |
| US6768078B1 (en) | 2003-01-09 | 2004-07-27 | Fanuc Robotics North America, Inc. | Servo spot welding control system and method of welding workpieces |
| KR100837923B1 (en) * | 2006-12-13 | 2008-06-13 | 현대자동차주식회사 | Variable stroke typed welding gun for welding robot |
| JP5521421B2 (en) * | 2009-07-21 | 2014-06-11 | スズキ株式会社 | Double welding gun structure |
| KR101230991B1 (en) * | 2010-11-12 | 2013-02-07 | 기아자동차주식회사 | Pitch variable type twin spot welding apparatus |
| KR101248652B1 (en) * | 2010-12-31 | 2013-03-28 | 서진산업 주식회사 | Apparatus for Adjusting Pitch of Pitch Series Spot Welding Gun, Pitch Series Spot Welding Gun including the Apparatus for Adjusting Pitch and Welding Method using the Pitch Series Spot Welding Gun |
| DE102012008831A1 (en) * | 2012-04-28 | 2013-10-31 | Volkswagen Aktiengesellschaft | Joining of components by means of resistance welding |
| KR101382319B1 (en) | 2012-12-17 | 2014-04-08 | 현대자동차 주식회사 | Twin spot welding apparatus |
| US9238280B2 (en) | 2013-03-15 | 2016-01-19 | Honda Motor Co., Ltd. | Dual shift unit for welder |
| KR101448771B1 (en) * | 2013-03-26 | 2014-10-08 | 현대자동차 주식회사 | One side direction spot welding apparatus |
| KR101448772B1 (en) | 2013-04-03 | 2014-10-08 | 현대자동차 주식회사 | Spot welding apparatus |
| WO2015125991A1 (en) * | 2014-02-24 | 2015-08-27 | 주식회사 호원 | Hybrid welder |
| DE102014206437A1 (en) | 2014-04-03 | 2015-10-08 | Volkswagen Aktiengesellschaft | More spot welding gun |
| JP6393707B2 (en) * | 2016-04-28 | 2018-09-19 | 川崎重工業株式会社 | Spot joining apparatus, spot joining method and joint structure |
| CN106270996B (en) * | 2016-09-23 | 2018-08-24 | 苏州哈工易科机器人有限公司 | A kind of horizontal spot welding device for the welding of Frame lamp end |
| CN107738029A (en) * | 2017-09-30 | 2018-02-27 | 武汉捷众汽车零部件有限公司 | A kind of intelligent rush-harvesting and rush-planting mash welder |
| CN107695498A (en) * | 2017-10-20 | 2018-02-16 | 南京泓凯动力系统科技有限公司 | A kind of automatic soldering device of automobile body-in-white |
| CN109015711A (en) * | 2018-08-15 | 2018-12-18 | 长春森酉科技有限公司 | A kind of multi-function robot and intelligent production line |
| CN112338340A (en) * | 2020-10-29 | 2021-02-09 | 昆山点溶智能科技有限公司 | Single-face double-spot welding gun |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1434374A (en) * | 1922-11-07 | Poration | ||
| US1189584A (en) * | 1915-04-05 | 1916-07-04 | Charles H Kicklighter | Apparatus for and method of electric fastening of metals. |
| US4291214A (en) * | 1978-12-19 | 1981-09-22 | Bra-Con Industries, Inc. | Welding apparatus having closely mounted shunts |
| JPS5910983U (en) * | 1982-07-09 | 1984-01-24 | 本田技研工業株式会社 | Power supply device for resistance welding gun |
| US4496821A (en) * | 1982-08-06 | 1985-01-29 | Marelco Power Systems, Inc. | Transformer for robot arms |
| DE3344631A1 (en) * | 1982-12-24 | 1984-07-05 | Honda Giken Kogyo K.K., Tokio/Tokyo | WELDING GUN DEVICE |
| JPS6066681U (en) * | 1983-10-05 | 1985-05-11 | 日産自動車株式会社 | Dual type spot welding gun |
| JPS6142696A (en) * | 1984-08-06 | 1986-03-01 | 三菱電機株式会社 | Scale display unit |
| JPS6187686A (en) * | 1984-10-05 | 1986-05-06 | Shin Etsu Chem Co Ltd | Method of separating and recovering hexamethyldisiloxane |
| JPH0324298Y2 (en) * | 1984-11-15 | 1991-05-27 | ||
| JPS61143775U (en) * | 1985-02-27 | 1986-09-05 | ||
| JPH0630822B2 (en) * | 1985-12-28 | 1994-04-27 | 東急車輌製造株式会社 | Multi-axis spot welding equipment |
| JPS62137682U (en) * | 1986-02-20 | 1987-08-29 | ||
| GB8616164D0 (en) * | 1986-07-02 | 1986-08-06 | Shell Int Research | Hydrocarbyl-grafted cellulose fibres |
| JPS63224879A (en) * | 1987-03-12 | 1988-09-19 | Kikuchi Press Kogyo Kk | Multiple spot welding robot |
-
1989
- 1989-03-20 JP JP1065975A patent/JP2580029B2/en not_active Expired - Fee Related
-
1990
- 1990-03-19 EP EP90904664A patent/EP0418395B1/en not_active Expired - Lifetime
- 1990-03-19 KR KR1019900701955A patent/KR930004998B1/en not_active IP Right Cessation
- 1990-03-19 DE DE69009130T patent/DE69009130T2/en not_active Expired - Fee Related
- 1990-03-19 US US07/613,781 patent/US5111019A/en not_active Expired - Fee Related
- 1990-03-19 WO PCT/JP1990/000366 patent/WO1990011160A1/en active IP Right Grant
- 1990-03-19 CA CA002028812A patent/CA2028812A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| US5111019A (en) | 1992-05-05 |
| DE69009130T2 (en) | 1994-11-17 |
| KR930004998B1 (en) | 1993-06-11 |
| DE69009130D1 (en) | 1994-06-30 |
| JPH02247083A (en) | 1990-10-02 |
| WO1990011160A1 (en) | 1990-10-04 |
| EP0418395A4 (en) | 1992-05-06 |
| KR920700090A (en) | 1992-02-19 |
| JP2580029B2 (en) | 1997-02-12 |
| EP0418395B1 (en) | 1994-05-25 |
| EP0418395A1 (en) | 1991-03-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 19920919 |