Grid welding machine and method for producing wire grids

A grid welding machine, comprising:

• the grid welding machine operable continuously based on an electrical resistance principle,
• a stationary longitudinal frame, whereon a horizontal group of parallel longitudinal wires are movable continuously in a production direction by a feeding device, and
• a pulling-off device, by which cross wires are pullable off a coil or rings and fed transversely to the group of longitudinal wires in a transfer device extending transversely, which transfer device is configured to pick up the cross wires and convey the cross wires one after another towards the longitudinal wires and bring the cross wires into contact with the longitudinal wires in a correct orientation according to a scaling of the cross wires and drop the cross wires upon contact with the longitudinal wires, and
• upper electrodes and lower counter electrodes each having a weld surface, respectively, the weld surfaces of which are pressable against each other with points of intersection formed between the longitudinal wires and the cross wires therebetween to form a grid,
• wherein both the upper electrodes and the lower counter electrodes are arranged on an inner frame mounted to the stationary frame and movable back and forth periodically in a longitudinal direction relative to the stationary frame, and the upper electrodes are mounted to the inner frame for movement from an upper position downwards onto the points of intersection formed between the longitudinal wires and the cross wires,
• wherein the upper electrodes are movable downwards from the upper position to reach a first position of a beginning welding process in contact with the points of intersection formed between the longitudinal wires and the cross wires and then, while maintaining contact pressure, travel along by moving the inner frame in the longitudinal direction together with the lower counter electrodes traveling from a first position and synchronously with the grid into a second position of an ending welding process, which is at a same height level and in a rear with respect to a direction of flow, the upper electrodes and the lower counter electrodes then returnable to the first positions, respectively, with respect to the longitudinal direction again by moving the inner frame back, while the upper electrodes are movable vertically upwards and then again downwards into the first position of the beginning welding process of following cross wires,
• wherein the cross wires are bringable into contact with the group of longitudinal wires in the correct orientation by gripping fingers,
• wherein the gripping fingers are movable to the transfer device and then movable together with one of the cross wires picked-up by the transfer device towards the longitudinal wires until the cross wire contacts the longitudinal wires to form the points of intersection at a time before the upper electrodes arrive at the first position, and
• wherein the gripping fingers, by the movable inner frame, first travel alone along a first section of a travel path of the inner frame before welding begins and then together with the upper electrodes and the lower counter electrodes travel along another section of a horizontal path synchronously with the longitudinal wires, whereupon the synchronous travel of the upper electrodes and the lower counter electrodes is continuable until welding is completed.