Welding apparatus using transformer with movable secondary and its method of manufacture and use

A method of welding a workpiece with a welding apparatus having a transformer having a U-shaped secondary winding movable therein, and first and second electrodes each being electrically connected to one of the legs of the secondary winding;

• the method comprising the steps of:
• (a) moving the first electrode towards the workpiece so as to contact the same, the first electrode being flexibly connected to one leg of the secondary winding;
• (b) moving the second electrode towards the workpiece so as to contact the same, the second electrode being rigidly connected to the other leg of the secondary winding whereby the secondary winding within the transformer is guided by the movement of the secondary electrode;
• and
• (c) effecting the weld.

Resistance welding apparatus comprising:

• (a) a casing on which is mounted a stationary primary winding for a connection to a source of alternating current;
• (b) a U-shaped secondary winding having a pair of spaced apart legs, said secondary winding being magnetically coupled to said primary winding and mounted for movement relative thereto;
• (c) an actuatable fluid operated jack having a cooperable piston and cylinder movable relative to each other and to said casing;
• (d) a first welding electrode on said cylinder and a second welding electrode on said piston for clamping a workpiece therebetween;
• (e) a flexible conductive shunt connecting one leg of said secondary winding to said second electrode;
• and
• (f) a rigid conductive connector connecting the other leg of said winding to said first electrode.

Resistance welding apparatus comprising;

• (a) a casing in which is mounted a stationary primary winding;
• (b) a rigid secondary winding magnetically coupled to said primary winding and mounted for movement relative thereto;
• (c) a fluid actuated cylinder containing a piston that moves in response to pressurization of the fluid;
• (d) means mounting said cylinder on said casing for movement relative thereto;
• (e) a first electrode rigidly connected to said piston and having a flexible conductor connected to one end of said secondary winding;
• (f) a second electrode rigidly connected to said cylinder and to the other end of said secondary winding;
• and
• (g) stop means on said piston cooperable with stop means on said casing for limiting movement of said piston in one direction.

A method for welding a workpiece using apparatus comprising a casing in which is mounted a stationary primary winding;

• a rigid secondary winding magnetically coupled to said primary winding and mounted for movement relative thereto;
• a fluid actuated cylinder containing a piston that moves in response to pressurization of the fluid;
• means mounting said cylinder on said casing for movement relative thereto;
• a first electrode rigidly connected to said piston and having a flexible conductor connected to one end of said secondary winding;
• a second electrode rigidly connected to said cylinder and to the other end of said secondary winding;
• and stop means on said piston cooperable with stop means on said casing for limiting movement of said piston in one direction, said method comprising the steps of:
• (a) pressurizing one side of said cylinder when said stop means on said piston and on said casing are in cooperation for effecting movement of said piston in a direction opposite to said one direction whereby said first electrode moves toward said second electrode into engagement with said workpiece when the latter is inserted between said electrodes;
• (b) continuing pressurization of said one side of said cylinder after said workpiece is engaged by said first electrode for effecting movement of said cylinder relative to said workpiece until the second electrode clamps said workpiece to said first electrode;
• (c) applying a welding pulse to said primary winding for effecting a spot weld of said workpiece;
• (d) pressurizing the opposite side of said cylinder to effect movement of the piston relative to the cylinder and disengagement of said first electrode from said workpiece until the stop means on said piston operatively engages the stop means on said casing;
• and
• (e) continuing pressurization of said opposite side of said cylinder to effect movement of said cylinder relative to said casing whereby the workpiece is disengaged from said electrodes.