1. Field of the Invention
This invention relates a parts welding device, wherein a part, such as a bolt, is held by a spring chuck mean and the part is welded to the other part, such as a steel plate.
2. Description of Related Art
As a method of welding a bolt where a flange is integrally formed on the shaft to a steel plate, stud welding is known. In this method, a collet-type chuck with a spring structure is arranged on the head of a feed pipe for the bolt and the shaft of the bolt moved to the chuck is held by the spring structure, wherein the flange is exposed on the head side. The flange is brought closer to the steel plate, and welding current is made to flow between the flange and the steel plate to generate arc, which fuses the flange and steel plate together by metal fusion. Then, pressure welding follows, completing the welding process.
The above method is to hold the bolt after stopping the approaching bolt by the collet-type chuck. This method, however, raises the problem that the holding position of the bolt is not determined in a constant manner. In such a situation, the gap between the flange and steel plate becomes not constant, causing the unevenness of welding quality. Further, for automating such a welding system, feeding and holding the bolt in a secure manner upon welding is imperative, but the above method cannot provide an operation enabling the feeding and holding to be made in a satisfactory manner. Besides, in the case of a nut with a flange integrally formed on the cylindrical part of the nut, on the internal surface of which a female screw is formed, a similar problem occurs when the flange is welded to the other part.
This invention is a parts welding device provided to solve the problem mentioned above. In the invented system, a part feed apparatus and a welding apparatus are mounted on a board, a supporting member is fitted on a supporting shaft fixed on the board in a rotary manner, a welding unit is fitted into the supporting member, and a receiving hole for a part fed by the part feed apparatus is formed on the head of the supporting shaft, wherein the head tip of the welding unit is arranged near the opening of the receiving hole.
The part fed by the part feed apparatus is inserted into the receiving hole and held there, and the part comes in contact with the other part, then both parts are welded together by the welding unit. The supporting shaft has the opening as the receiving hole for the part and the supporting member is fitted on the supporting shaft in a rotary manner, that is, the supporting member equipped with the welding unit is fitted on the supporting shaft in a rotary manner. Therefore, the operations, such as holding the part in the receiving hole and fitting or rotation of the welding unit, are arranged in a compact manner while the supporting shaft is set as the central member for the operations, providing a welding system having a constitutional advantage. In addition, when the part is fed to the receiving hole, the part is inserted in the hole from the outside, so that it can be held with the supporting shaft in a smooth manner.
It is applicable that the above supporting member is rotated by a rotation mean so that the head tip is moved to a prescribed position. As the supporting member rotates, the welding unit fitted into the supporting member rotates together, allowing the head tip to move freely to a required welding spot. Therefore, when a circular flange is welded to a steel plate, local welding spots can be arranged apart at 120 or 180 degree without fail.
While the above supporting shaft is arranged in the direction almost perpendicular to the board and the above part feed apparatus inserts the part retained on the feed rod of the feed unit into the above receiving hole from the head side of the above supporting shaft, a retaining mean for the part may be arranged in the above receiving hole. As described above, the part feeding behavior is to inserting the part into the receiving hole form the head side of the supporting shaft, wherein part holding can be made by the most simple method of inserting the part from the outside. As a result, the dislocation of the holding position of the part never occurs, making the relative position between the part and the other part constant, thus a good welding quality can be obtained. Further, arranging the part holding mean in the receiving hole keeps the relative position between the receiving hole and the part constant, maintaining a correct contact state upon making the part come in contact with the other part, thus works effectively to improve welding quality.
While the feed rod of the above part feed apparatus is made to move back and forth in an inclined state against the above supporting shaft, a moving-back-and-forth mean may be arranged for moving back and forth the whole body of the above feed rod in the same direction of the axis of the part retained on the feed rod. The part retained on the head of the inclined feed rod stops in the position where the axes of the part and receiving hole are aligned. Then, the whole body of the feed rod moved in the axial direction of the receiving hole and the part, allowing the shaft of the part to be inserted smoothly into the receiving hole. As described here, by arranging a proper position relation between the feed rod and supporting shaft and moving the whole body of the feed rod, the above smooth operation can be achieved, so that a high credibility as a welding system can be maintained. In order to secure the above coaxial state between the shaft and receiving hole, in this system, the axis of the supporting shaft, the axis of the shaft held by a supporting pipe, and the stroke direction of the piston rod of an air cylinder are all set in parallel. Thus, when the whole body of the feed rod is moved, the shaft is inserted smoothly in the receiving hole.
The above board can be fitted on the head of a robot apparatus. By operating the robot apparatus, the board is moved freely to any directions and the direction of the board upon its stopping can be selected freely, the parts welding can be made without any hamper even if the other part has a complicated form or the welding point is in a complicated area. In addition to such a free moves of the board, the particular arrangement made for the supporting shaft and feed rod gives more advantages to this welding system, further enhancing the utility of the system.
In another application, the above board is fixed to a stationary member and the other part to which the part is welded is held with the robot apparatus. Such a constitution is reverse to the one mentioned above, but secures the same advantages obtained by the one mentioned above. In the reversed constitution, the other part is held with the robot to move freely, while the part feed apparatus and the welding apparatus are kept stationary.