ROBOT WELDER

Abstract: A robot type resistance welder of very large capacity that enables the electrodes (1, 2) of the welder to be readily adjustable in the welding and retracting strokes and automatically controlled so as to retract when encountering an obstacle - also whereby the degree of retraction of electrodes may be selectively controlled and whereby the vertical elevation of the work plane may be varied during welding in accordance with the contour of the work, such as a curved panel. The respective electrodes (1, 2) of the spot welders have supporting arms (3, 4) which are pivotally interconnected together with an operating air cylinder (10). An adjustable stop (16) is provided in the air cylinder (10) to adjust the extend of retraction. The entire assembly including the pivotal supporting arms (3, 4) and inter-connected cylinder (10) are provided with an adjustable stop (17) for limiting the pivotal movement of the assembly. Such pivotal movement is cushioned by springs. By preprogramming spot welding, automatic welding in a very short time can be accomplished on a wide variety of panel shaped objects while speedily producing welds of excellent quality.

Description: Robot Welder This invention relates to a "robot" type of spot welder of high capacity. Resistance spot welding "robots" currently in use have limited capacities in throat depth, weld force and weld current due to limited weight that can be supported at the end of the "robot" arm. An object of the present invention is to over¬ come the above-named disadvantages insofar as panel welding is concerned, and to incorporate "robot" performance in a snot welder of such construction that it can be built in very large sizes a d welding capacities, far exceeding that of any "robot" welder heretofore devised. Another object of the invention is to provide a novel resistance welder, particularly suitable for "robot" operation and embodying electrodes having variable working strokes, retraction strokes and as well as variable electrode elevation adjustment, with the capability of making both the working strokes and retracting strokes of one electrode different from that of the other to allow clearing o^ obstancles while in the course of preprogrammed spot welding, Other objects and advantages of the invention will OMPI become more apparent from a study of the following description, taken with accompanying drawing wherein: Fig. 1 is a side elevational view of "robot" type spot welding machine embodying the present invention. Referring more particularly to Fig. 1 of the draw¬ ing, numerals 1 and 2 denote a pair of welding elec¬ trodes supported by horns 3 and 4, respectively which are integrally connected to supporting arms 5 and 6 respectively, which are both pivotally mounted on a central pivot shaft 7, Connected to the top of arm 5 is a piston rod 8 which is connected to a piston 9 contained within air cylinder 10. Such cylinder is mounted on a trunnion or pivot on the housing of cylinder 10 and is pivotally supported by an upper integral extension 6b of horn 6. In operation, when air under pressure is intro¬ duced in cylinder 10 between pistons 9 and 15, piston 9 will move to the left, as viewed in Fig. 1, and will cause horns 3 and 4 and electrodes 1 and 2 to move towards the work W. As the electrodes 1 and 1 contact the work W, spot welding occurs from current flowing through the high current capacity secondary shunts of a stationarily mounted transformer (not shown). OMPI After welding, when air is introduced into the left side of piston 9, both horns 5 and 6 will move about pivot shaft 7 as a center, in an opposite dir¬ ection than that already described, thereby retract¬ ing electrodes 1 and 2 from work W until piston 9 comes against the adjustable piston stop 15„ Such piston is adjusted by turning the adjusting handle 16. Piston 15 is held in position by air pressure on the rod side. When it is necessary to clear an obstacle, such air pressure is exhausted allowing piston 9 to move piston 15 to the right until it hits bottom. The amount of the retraction assigned to the upper electrode is controlled by adjusting jackscrew 21 in or out as desired, When the retraction stroke is used, jackscrew 21 will contact fixed stop 22 which will limit the stroke of the upper electrode. The remainder of the total stroke goes to the lower electrode. For example, if the total stroke is 5" and stop 22 is adjusted so that the upper electrode strokes 2", then the lower electrode will stroke 3" , Instead of having equal working and retracting movements of electrodes 1 and 2, they may be varied so that one electrode may have a greater working, as well as a greater retracting movement than the other. An adjustable link type stop is selectively driven back and forth, through cushioning spring by a D_ C. stepping motor 20 and screw rotated thereby, This will provide a means of adjusting and programming the elevation of the electrodes 1 and 2 in the Z direction, in order to weld on different pla.nes, such as a contour or a panel with steps. If stop 17 is driven to the left, both upper and lower electrodes 1 and 2 will move up the same amount, This feature has nothing to do with the weld stroke or retraction stroke. The elevation (height from the floor) of the elect¬ rodes 1 and 2 is preprogrammed. This is accomplished by allowing the entire assembly, comprising parts 1, 2, 3, 4, 5, 6, 6b and 10 to rest, as a unit, against adjustable stop 17. Stop 17, in turn, can be driven to the left or right by D. C. stepping motor 20. If the stop is moved to the left, it will cause the entire assembly to rotate about pivot shaft 7 in a clockwise direction. This rotation will move elect- O PI rodes 1 and 2 upwardly. Moving stop 17 to the right will have the opposite effect. This travel may be limited to plus or rainum 2 inches or a total of 4 inches on a particular machine. In short, the above described adjustment is vertically, in the Z dir¬ ection for the work W_ Of course, if manual instead of automatic adjustment is desired, rod 18 may be adjustably moved horizontally such as by a carriage. To adjust the electrodes 1 and 2 horizontally, carriage 22 is driven in the X direction, to the right or left, by the X drive motor. To adjust hori¬ zontally at right angles thereto, in the Y direction, a lower carriage 24,25 is selectively driven on tracks 26 in either direction. Thus the electrodes 1 and _. are selectively adjust¬ able in the X Y and Z directions, at right angles to each other. If a five inch stroke is available, it can be divided, as described, between the working stroke and the retraction stroke, - say two inches of working stroke and three inches of retraction stroke. Such larger retraction strokes are used to clear obstruct¬ ion when indexing. Then the welding strokes can be divided, as desired, between the upper and lower elect- rodes, — say one-half inch stroke of the upper electrode 1 and one and one-half inch stroke for the lower electrode 2. Of course, these figures can be reversed simply by moving programmable stop 17 oppositely to the right. Since the weight of the welding machine can be supported by two heavy X-Y direction floor (at right angles) mounted slides the size of the welding trans¬ former and welding force system of almost no limit is obtainable as compared to resistance welding "robots" on the market today. They are very limited in the weight they can carry due to their particular suspen¬ sion system, such as a cantilever system. Typical parameters of the present welder are a weld force of 2000 lbs. at 80 psi air, 24000 amps short circuit, 100 KVA transformer 90" "travel in the Y axis and 30" travel in the X axis and 3 inch travel in the Z axis", The electrode retraction feature can be pre-set so as to be used on the upper electrode 1 only, or on the lower electrode 2 only, or it can be divided between the upper and lower electrodes. After a weld is made, and the electrodes are re¬ tracted, the welding unit, including the transformer, is moved to the next weld location by energizing either the X drive motor or Y drive motor or both. Both motors are preferably closed loop resolver feed¬ back D β C. servomotors which drive the carriages in the X direction and in the Y direction (at right angles thereto) through linear ball screws. Also, an addition to direction of movement in the Z direction may be pro¬ vided by moving stop 17 through closed loop D. C. motor 20, The spot weld locations, weld schedules and sequ¬ encing may be accomplished by means of a programmable controller, Thus it is possible to weld a door which is either flat or curved and to sequentially spot weld nuxαerous parts thereto of different sizes by properly choosing, during programming, the proper weld strokes and retraction strokes of *=ach of the respective elec¬ trodes 1 and 2. The welding machine can weld, index and weld over 500 preprogrammed spot'? on a panel The spot welding schedules of squeeze time, weld time, current and welding force can be pre-programmed from a choice of 20 schedules or so. By virture of such programming by teach pendent or tape, a wide variety of weld programs can be accompli¬ shed to spot weld a complete piece of work in _. O PI fraction of the time it normally takes to weld. Moreover, unusual shaped items, such as a curved door panel may be spot welded very speedily to many appurentenances, such as hinges, brackets, angles, channels, latches and the like. It is useful to weld train doors, bus doors, vending machine doors and panels, copy machine panels, electrical control panels, etc. Thus it will be seen that I have provided a "robot" function to a very heavy duty resistance spot welder by virtue of the pivotal assembly described above, includ¬ ing various adjustments for varying working strokes and retracting strokes of the elect odes; furthermore, I have provided an extremely high speed programmed spot welder, not heretofore possible in a large welding mach¬ ine which enables its performance to out-match that of any existing welders of high capacity and rating, there¬ fore considerably increasing production and thereby greatly reducing the cost for welding various items; also, since the weight of the present welder is suoported by two h^avy X-Y floor mounte slides, there is almost no limit as to the size of the welding transformer and welding force system. While I have illustrated and described a single embodi- OMPI ment of ray invention , it will be understood that this is by way of illustration only and that various changes and modifications may be contemplated in my invention and within the scope of the following claims . • *_? ?„

Claims: I CLA IM: 1. A resistance welding machine comprising a pair of confronting welding electrodes for welding a work therebetween, a pair of elongated pivotally mounted horns for supporting large panels therebetween, each supporting one of said electrodes, an air operating cylinder enclosing a pair of pistons, one of said pistons pivotally connected to one of said horns, the other of said pistons having means for adjusting its longitudinal position in said cylinder, said cylinder being connected to the other of said horns, a fixed stop means for adjustably limiting pivotal movement of said one of said boms , stepping motor means for selectively driving, in opposite directions, said other of said horns, -.nd means fπr selectively adjusting the piston of ?aid electrodes -in a vertical and horizontal plane compri <3 ing motor driven carriages in stacked relationship, whereby adjustment in three planes at right angles to each other is provided, said electrodes and horns being located directly above said carriages, 2, A machine as recited in claim 1 wherein said stepping motor means comprises an arm resilientlv mounted on a pivotal stop and a D. C. stepping motor selectively pivoting said arm in either direction, T f ° MPI

Inventors: CHALLENGER RICHARD, CHALLENGER, RICHARD
Applicants: TAYLOR WINFIELD CORP, THE TAYLOR-WINFIELD CORPORATION
Application year: 1984
Main classification: B23K11
IPC codes: B23K11