The invention relates to a spot welding cap changer (1) with a cap puller (2) and two cap magazines (3, 3A), the cap puller (2) having a gripper (20) with spring-loaded, pivotable jaws (21, 22), which in response to a turning and axial pulling-off movement detaches a spot welding cap (K) of a pincer spot welding head introduced into it from a shaft of the pincer welding head in such a way that it is clamped to prevent it twisting, and the cap magazines (3, 3A) holding spot welding caps respectively in a round cap carrier (31) such that they are circularly arranged in a directed and oriented manner and are respectively transported individually one after the other into an access position against a stop (32) by an advancing force (P).

A first electrode coolant path is configured to cool a first welding electrode by liquid coolant flowing from a supply path through the first electrode coolant path to a return path. A second electrode coolant path is configured to cool a second welding electrode by liquid coolant flowing from the supply path through the second electrode coolant path to the return path. Three or more valves are configured to stop or reduce liquid coolant flow through the first or second electrode coolant path and configured to stop or reduce liquid coolant backflow from the return path when the first or second welding electrode is at least partially detached. At least one valve is coupled in the first or second electrode coolant path. A drawback apparatus generates a suction force to draw liquid coolant away from a gap formed when the first or second welding electrode is at least partially detached.

A first electrode coolant path is configured to cool a first welding electrode by liquid coolant flowing from a supply path through the first electrode coolant path to a return path. A second electrode coolant path is configured to cool a second welding electrode by liquid coolant flowing from the supply path through the second electrode coolant path to the return path. Three or more valves are configured to stop or reduce liquid coolant flow through the first or second electrode coolant path and configured to stop or reduce liquid coolant backflow from the return path when the first or second welding electrode is at least partially detached. At least one valve is coupled in the first or second electrode coolant path. A drawback apparatus generates a suction force to draw liquid coolant away from a gap formed when the first or second welding electrode is at least partially detached.

The present invention relates to a direct-contact type alternating current (AC) trapezoidal wave aluminum resistance welding process method. AC trapezoidal wave inverter controller capable of controlling a positive and negative half-wave current rising rate, and an AC transformer (no rectifier or silicon-controlled rectifier on a secondary coil of the transformer) with an output voltage of 10-30V, a peak current of 32-70 kiloampere and a frequency of 25-80 Hz are included. The inverter controller and the AC transformer are connected by means of a conductor, a welding electrode, a pressurization mechanism and a cooling system to form resistance welding equipment to enable the equipment to output positive and negative alternating trapezoidal wave current on two sides of the electrode when a workpiece is pressurized and welded and to perform welding according to a specified duty ratio, welding current, frequencies, welding cycle number and welding pressure. Practice proves that the method has the advantages that 50-150 welding spots can be welded while grinding the electrode once each time, service life of the electrode is prolonged by 2-5 times, production efficiency and welding quality are greatly improved, and production cost is reduced, thereby realizing a qualitative leap in aluminum and aluminum alloy resistance welding processes.

A spot welding method is a method of performing spot welding to obtain a spot welded joint, the method including a spot welding with two-stage welding, setting a ratio (I.sub.2/I.sub.1) of a current I.sub.2 of a second welding process to a current I.sub.1 of a first welding process to from 0.5 to 0.8, setting a time tc of a cooling process within a range of from 0.8tmin to 2.5tmin wherein tmin is calculated using the equation (0.2H.sup.2) according to a sheet thickness H of the steel sheets, setting an welding time t2 of a second welding process within a range of from 0.7tmin to 2.5tmin, and setting a pressure from the cooling process onward to greater than a pressure until the first welding process.

An electrode device for water-cooling type resistance welding that constantly circulates cooling water efficiently to the proximity of an electrode tip, allowing the electrode to stably cool down. A cooling pipe 11 is inserted inside a device body 1 from a lower side thereof, and cooling water ejected from a tip opening 11a of the cooling pipe 11 cools a cap tip 10 placed on the tip of a shank 8. The cooling pipe 11 is movable in the axial direction of the device body 1 and fixable at any position. As a result, even with a change in the length of the shank 8, the tip opening 11a of the cooling pipe 11 can always be positioned in the proximity of the cap tip 10, allowing the cap tip 10 to cool down reliably and the form of the electrode tip to be maintained stably for a long time.

The invention relates to a spot welding cap changer (1) with a cap puller (2) and two cap magazines (3, 3A), the cap puller (2) having a gripper (20) with spring-loaded, pivotable jaws (21, 22), which in response to a turning and axial pulling-off movement detaches a spot welding cap (K) of a pincer spot welding head introduced into it from a shaft of the pincer welding head in such a way that it is clamped to prevent it twisting, and the cap magazines (3, 3A) holding spot welding caps respectively in a round cap carrier (31) such that they are circularly arranged in a directed and oriented manner and are respectively transported individually one after the other into an access position against a stop (32) by an advancing force (P).

A first electrode coolant path is configured to cool a first welding electrode by liquid coolant flowing from a supply path through the first electrode coolant path to a return path. A second electrode coolant path is configured to cool a second welding electrode by liquid coolant flowing from the supply path through the second electrode coolant path to the return path. Three or more valves are configured to stop or reduce liquid coolant flow through the first or second electrode coolant path and configured to stop or reduce liquid coolant backflow from the return path when the first or second welding electrode is at least partially detached. At least one valve is coupled in the first or second electrode coolant path. A drawback apparatus generates a suction force to draw liquid coolant away from a gap formed when the first or second welding electrode is at least partially detached.

A sliding member integrated with a guide pin is inserted into a guide hole of an electrode main body. An elastic ring is integrated with the guide pin under a state in which the guide pin passes through the elastic ring. A portion of the sliding member has a pressurizing end surface configured to press the elastic ring against an inner end surface of the guide hole. When the pressurizing end surface presses the elastic ring against the inner end surface, flow of the cooling air is interrupted. When the elastic ring is away from the inner end surface, the cooling air is allowed to flow.

A first electrode coolant path is configured to cool a first welding electrode by liquid coolant flowing from a supply path through the first electrode coolant path to a return path. A second electrode coolant path is configured to cool a second welding electrode by liquid coolant flowing from the supply path through the second electrode coolant path to the return path. Three or more valves are configured to stop or reduce liquid coolant flow through the first or second electrode coolant path and configured to stop or reduce liquid coolant backflow from the return path when the first or second welding electrode is at least partially detached. At least one valve is coupled in the first or second electrode coolant path. A drawback apparatus generates a suction force to draw liquid coolant away from a gap formed when the first or second welding electrode is at least partially detached.