Abstract: A shell mold includes a plurality of sleeve forming portions. Of the sleeve forming portions, at least an endmost sleeve forming portion located adjacent to a subrunner portion has a modified shape for compensating for deformation of cast sleeves caused by solidification and contraction of molten metal. A shell molding apparatus includes an upper die and a lower die which constitute a die set for molding a shell mold. The lower die is composed of shell molding inserts, each having the shape of a halved cylinder, spiny insert receiving recesses formed in the shell molding inserts, and spiny inserts retractably provided in the spiny insert receiving recesses. In a casting method using a shell mold, many protrusions of a spiny insert are reversely copied to the inner surface of a halved shell mold at the undercut portion of the inner surface, thereby forming many depressions at the undercut portion. The halved shell mold is parted from the lower die.

Abstract: A robot welding gun comprises a welding gun mounting bracket provided at the tip end of a robot arm, a cylinder unit incorporated in the bracket for adjusting the position of a fixed arm, a rod which is rotated or moved forward or backward by the cylinder unit and is connected to the fixed arm and a gun body which include the arm and is slidably mounted on the mounting bracket. As a result, it is possible to eliminate the variation of movement of the welding gun caused by the robot by adjusting the position of the welding gun relative to the fixed arm in accordance with the wearing amount of an electrode of the welding gun on the side of the fixed arm to always keep the same in contact with a surface of a weldment so as to provide a robot welding gun unit easy in control and capable of safe and accurate welding without generating distortion in the weldment.

Abstract: A resistance welding control method capable of reducing generation of spatter to the utmost during consumption of electrodes, thereby obtaining a desired nugget and assuring excellent welding quality and controlling with ease.

Abstract: A method of and apparatus for dressing tips for welding machines equipped with tips which are advanced toward a dresser body so as to be dressed by the cutters of the dresser body at a pressurized state. The method comprises the steps of driving to rotate the cutters before the tips are brought into contact with the cutters, pressing the tips to the cutters so that the dressing of the tips starts by being cut by the cutters while the tips are brought into contact with the cutters at a given time, moving the tips away from the cutters while the cutters keep to rotate, and completing the dressing of the tips by gradually reducing the application of the pressure to the tips. The Apparatus comprises elements to embody the method.

Abstract: A connection member in a welding gun for a robot having a cradle of the welding gun generates less stress by directly connecting the cradle with a robot wrist, whereby the welding gun is positioned as close as possible to the robot wrist. The welding gun for robot can be shortened by accommodating a welding transformer inside a hollow frame defined in the cradle.

Abstract: A welding gun provided with a backup cylinder is characterized in that the welding gun is moved toward a workpiece by a welding robot an end of which is connected to the welding gun via a bracket, then one electrode is brought into contact with the workpiece by a backup cylinder so that the workpiece is held by one electrode, thereafter the other electrode is brought into contact with the workpiece by a pressure application cylinder so that the pressure force is applied to the workpiece by both the electrodes for welding operation.

Abstract: A tool changer for welding robot comprising: male portions of connectors provided at a substrate fixed to a robot arm side for supplying electricity, gas, air, water to the tool side from the robot arm side; and female portions of connectors to be connected to the male portions of the connectors and provided at a substrate fixed to a tool side for receiving electricity, gas, air, water from the male portions of connectors, characterized in that one pair or plural pairs of connectors serve both the connectors and a guide mechanism composed of a guide pin and a guide receiver.

Abstract: A tool changer for welding robot comprising: detachable male portions of connectors provided at a substrate fixed to a robot arm side for supplying electricity, gas, air, water to the tool side from the robot arm side; and detachable female portions of connectors to be connected to the male portions of the connectors and provided at a substrate fixed to a tool side for receiving electricity, gas, air, water from the male portions of connectors, each female portion composed of the connector, a protective tube provided at the substrate fixed to the welding gun side, a coupler inserted inside thereof, and an O-ring provided between the protective tube and the coupler, wherein the connector and the coupler are integrally formed and are radially slidable within the protective tube around the O-ring. A transformer is provided centrally of the connectors on the robot arm side substrate.

Abstract: A cutter of a tip dresser for welding gun has three blades, one of which is extended to a central position of the cutter and includes a flat portion and an upstanding portion. A cutting edge is formed on the flat portion reaching from the central position to the upstanding portion. With such arrangement of the cutter, the tip is satisfactorily cut by the cutting edge even in the vicinity of the central position where its circumferential speed is slow.

Abstract: A current sensor assures the detection of a current flowing through a welder conductor without requiring a particular power source, and indicates the current state with the aid of a lamp. In one embodiment, a welder conductor penetrates a toroidal core across which connects a slider resistor whose sliding arm connects through a rectifier circuit, and a parallel circuit of a capacitor and a resistor, to a lamp. A second embodiment imterposed between the parallel circuit and lamp wherein a series circuit of a second resistor and a Zener diode, and a transistor base is connected to a connection point between the second resistor and a Zener diode, and the emitter-collector circuit of which transistor drives the lamp. A third embodiment adds a further series circuit of another lamp and resistor across the parallel circuit and across the series circuit of the second resistor and the Zener diode.

Abstract: A welding machine controller for controlling the welding operation of a welding machine controls welding force applied to a workpiece by directly controlling a pressure regulating valve which regulates the pressure of working fluid supplied to a power cylinder for applying a welding force to the workpiece. The welding machine controller further controls squeeze time, welding time, hold time, OFF time, cooling time and welding current. The welding force is regulated in a single step or in a plurality of steps during one welding cycle according to the quality and/or thickness of the workpiece.

Abstract: A dressing device for a tip of a welding gun comprising a base; a dresser body; a driving device movably provided on said base for moving said dresser body; a pneumatic on-off valve connected with said dresser body; a control switch interposed between said driving device and the dresser body for controlling said pneumatic on-off valve; an air motor for rotating blades of said dressing device; a timer circuit responsive to pressure at an inlet of said air motor; an air changeover valve for changing over air to be fed to said driving device disposed on said timer circuit; a quick return mechanism mounted on said driving device; and a pneumatic control valve connected with said quick return cylinders and furthermore connected with said timer circuit, a tip of the welding gun can be dressed while setting thereof, at a prescribed position, by use of the quick return mechanism controlled by the timer without using springs.

Abstract: A resistance welding electrode includes a barrel-shaped portion having a cooling water passage defined therein and extending closely to an end surface thereof, and a cylindrical projection integrally formed on the end surface of the barrel-shaped portion. The cylindrical projection has a helical groove defined therearound, and may additionally have another helical groove defined therearound parallel to the first-mentioned helical groove in 180.degree.-out-of-phase relation thereto. The cylindrical projection may have an axial slot defined in its circumferential surface across the helical groove.