1. Field of the Invention
The present invention relates to an apparatus for machining a flash and upset material formed in a flash welding operation.
2. Description of the Prior Art
Heretofore it has been known to employ an apparatus for machining a flash and upset material formed in a welding operation, as shown in FIG. 1.
In FIG. 1, a stationary frame (3) and a movable frame (4) are disposed in the direction transferring workpieces (1),(2) and the movable frame (4) is shifted to the stationary frame (3) in the horizontal direction.
A lower stationary side electrode table (5b) and an upper stationary side electrode table (5a) are respectively fitted on the stationary frame (3). The upper stationary side electrode table (5a) is vertically shifted by a pressing device (7) to clamp the workpiece (1). The lower movable side electrode table (6b) and the upper movable side electrode table (6a) are also respectively fitted on the movable frame (4) and the upper movable side electrode table (6a) is vertically shifted by a pressing device (8) to clamp the workpiece (2).
The position of the movable frame (4) is controlled by an upset device (9).
After the completion of the welding operation, an upper tool holder (10) and a lower tool holder (11) which are waited out of the welding apparatus, are shifted to the direction of the welding line on the guide surfaces of the stationary side tool holder guides (14a),(14b) and the movable side tool holder guides (15a),(15b) whereby the flash and upset material is removed by machining with tools (12),(13) held by the upper tool holder (10) and the lower tool holder (11).
FIG. 2 is an enlarged view of the tool holder guides of FIG. 1.
In general, these welding apparatuses are used for welding various sheets from a thin sheet (about several mm) to a thick sheet (about several tens mm), and accordingly, a gap L between the electrode tables is varied at the starting and finishing depending upon the thickness of the sheet.
The operation will be illustrated.
The workpieces (1),(2) are clamped between the electrode tables with a predetermined gap being proportional to a thickness of the workpiece and then, the flash welding operation is started. The gap L between the electrode tables after the completion of the welding operation is too narrow in comparison with the space required for the machining of the flash and upset material, whereby it is difficult to machine the flash and upset material in this condition. The upper movable side electrode table (6a) is ascended after the welding operation, and the movable frame (4) is shifted to the space required for the machining of the flash and upset material and then, the upper movable side electrode table (6a) is descended to clamp the workpiece. If necessary, the upper stationary side electrode table (5a) is ascended and the workpiece is drawn out for a small distance by the movable side electrode tables (6a),(6b) and the welded part is departed for a small distance from the stationary side electrode tables (5a),(5b) and the movable side electrodes (6a),(6b) are backwardly shifted for a small distance to give a space for the gap l between the tool holder guides (14a),(14b), (15a),(15b). Thus, the welded part is shifted to the position between the electrode tables. As discussed above, it is necessary to vary the initial gap between the electrode tables from the final gap depending upon the size of the workpieces (1),(2). Various kinds of workpieces are usually welded by this type welding apparatus, whereby it may be necessary to vary the gap between the electrode tables depending upon the kind of the workpiece. That is, when large workpieces (1),(2) are welded, a size of the flash and upset material is large to be a wide gap between the electrode tables at the completion of the welding operation. On the other hand, when samll workpieces (1),(2) are welded, a size of the flash and upset material is small to be a narrow gap between the electrode tables at the completion of the welding operation. Accordingly, the space between the electrode tables is broadened to the space suitable for the machining.
As it is well-known significant large forces caused in the pressing of the workpieces are received by the electrode tables (5a),(5b), (6a),(6b), whereby the electrode tables are usually large and heavy and large pressing devices (7), (8) are needed and considerable time and energy are needed for the ascending, descending and shifting of the electrode table.
The time required from the completion of the welding to the machining of the flash and upset material is too long in the ascending, descending and shifting of the heavy electrode table whereby the temperature of the flash and upset material is lowered to harden the welded part and the resistance in the machining is increased and the standstill time for the line is prolonged, disadvantageously. Accordingly, in the conventional line, the machining of the flash and upset material has been carried out with 4 to 5 tools for each of the upper surface and the lower surface in order to attain the machining under high resistance in the machining.