Electric resistance welding head with electrodes located on the same side

Patent metadata

Field	Value
Publication number	US-10695859-B2
Application number	US-201715834583-A
Country	US
Kind code	B2
Filing date	Dec 7, 2017
Priority date	Feb 23, 2017
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

An electronically-controlled electric resistance welding head and method having a support structure and the electrodes located on the same side. The welding head including a ground electrode having an elastic device and a detecting device for detecting a force load on the elastic device on contact with a component to be welded. A welding electrode is movable relative to the ground electrode and the support structure to contact the component to be welded. An electronic control unit is operable to selectively increase the force applied by each electrode when in contact with the component to be welded until respective threshold values are achieved. Current is generated by a transformer for passage to the electrodes.

First claim

What is claimed is:

1. An electric resistance welding head with electrodes located on the same side, comprising:
a support structure having a connecting flange operable to connect to a wrist of an articulated robot;
an electric transformer connected to the support structure having two input poles operable to connect to electric supply cables and having two output poles;
a ground electrode and a welding electrode connected to the support structure and electrically connected to the two output poles of the electric transformer, said ground electrode further comprises a load-bearing element of electrically-conductive material, said load-bearing element having a front nose with a rounded end surface above to which a contact element is sited and retained, said contact element defines a rounded front surface selectively in contact with a component to be welded;
wherein said ground electrode and said welding electrode have respective main axes parallel to and spaced from each other, said ground and welding electrodes are movably mounted with respect to said support structure along the respective main axes;
an electrically operated actuator connected to said welding electrode, the actuator operable to move said welding electrode with respect to said support structure along the respective main axis;
said welding head further comprising:
a spring positioned interposed between said ground electrode and said support structure;
a detecting device operable to detect a load of the spring;
one or more electronic units operable to control the robot carrying said head and to control said welding head;
wherein said one or more electronic control units are further operable to:
control movement of the robot in order to move an end portion of said ground electrode in contact with the component to be welded, while maintaining said welding electrode in a retracted position with respect to said ground electrode;
continuing to control the robot movement in order to push said end portion of the ground electrode in contact with said component to be welded, causing an increase of the load of said spring until stopping the movement of the robot when the load of the spring reaches a predetermined threshold value, said contact element being relatively deformable, so as to recline itself on the component, increasing a contact surface defined by the rounded front surface, when said ground electrode is pushed in contact with the component to be welded;
after said stop of the movement of the robot, actuating said actuator to advance said welding electrode through a predetermined length, until reaching a predetermined position with respect to said support structure;
after reaching said predetermined position of said welding electrode, continuing to actuate said actuator for pushing an end portion of said welding electrode in contact with the component to be welded, so as to increase a force with which said actuator pushes said welding electrode in contact with the component until reaching a predetermined value of said force; and
after reaching said predetermined value of said force, supplying electrical current to said electrodes by means of said electric transformer for executing a resistance electric welding on said component.

2. The welding head according to claim 1 , wherein said detecting device of the load comprises a sensor operable to transmit an electric signal which is indicative of the load to said one or more electronic units.

3. The welding head according to claim 1 , wherein a distance between the main axes of said ground electrode and said welding electrode is adjustable.

4. The welding head according to claim 1 , wherein said load-bearing element is a carry-plait element and said contact element is a plait with one or more layers of electrically-conductive wires which are twisted one to each other.

5. The welding head according to claim 1 further comprising a bolt operable to connect said contact element to said front nose of said load-bearing element, said bolt passing through a hole defined by said front nose.

6. The welding head according to claim 1 further comprising:
said load-bearing element has a rear face located on an opposite part to said front nose, said rear face carrying a driving column operable to drive sliding movement of the ground electrode; and an electrically-insulating element positioned between the rear face and the driving column, said driving column being slidably mounted in a cavity defined by said support auxiliary body.

7. The welding head according to claim 6 , wherein said driving column comprises a bushing-like body having an outer surface slidably mounted within said cavity and an inner surface slidably mounted on a driving pin which is rigidly-connected to said auxiliary support body, said spring further comprising helical spring positioned within said bushing-like body between said driving pin and a bottom element rigidly-connected to the load-bearing element with the interposition of said electrically-insulating element, said detecting device of the spring load being interposed between said spring and said bottom element.

8. The welding head according to claim 6 , wherein the rear face of said load-bearing element carries, with the interposition of one or more electrically-insulating elements, an auxiliary anti-rotation pin operable to drive sliding movement of said ground electrode, said auxiliary anti-rotation pin being slidably mounted in an anti-rotation pin cavity defined by said auxiliary support body, said anti-rotation pin cavity being parallel to and spaced from the cavity in which said driving column slides, in order to prevent oscillations of the ground electrode around to the axis of said cavity wherein said driving column slides.

9. The welding head according to claim 1 further comprising at least one inlet conduit of coolant and at least one outlet conduit of coolant positioned within said support structure, wherein said at least one inlet conduit passes through said transformer, said ground electrode and said welding electrode, so as to cool them with said coolant.

10. The welding head according to claim 9 , wherein said at least one outlet conduit passes through said ground electrode and said welding electrode without passing through said transformer.

11. The welding head according to claim 1 , wherein said support structure further comprises two steel plates parallel to and spaced from each other, said two steel plates are rigidly-connected one to the other and parallel to a general plane defined by the two electrodes;
said transformer is mounted between the two plates;
said connecting flange further comprising:
a U-shape general configuration;
an end plate operable to be connected to the robot wrist, the end plate having a passage for tubes and cables for connecting the robot and the head; and
two parallel wings each respectively connected to one of said two steel plates of the support structure of the head, in such a way that said tubes and cables for connecting the robot and the head are not exposed to the external environment.

12. The welding head according to claim 11 , wherein said actuator further comprises a body mounted between the two steel plates of the support structure of the head; and an actuator rod driven through a passage defined by a bracket rigidly-connected to lower portions of said two steel plates of the support structure of the head.

13. The welding head according to claim 1 further comprising an outer case further comprising two lateral half-shells coupled one to each other, each of said half-shells having main walls which are parallel to a general plane defined by said support structur

Assignees

• Comau Spa

Inventors

• Gattabria Massimo
• De Chirico Cristina
• Marsicovetere Carmelo
• Maestri Mauro
• Di Stefano Giovanni

Classifications

• B23K11/25

  Monitoring devices · CPC title

• B23K11/11

  Spot welding · CPC title

• B23K11/255

  the measured parameter being a force (B23K11/253 takes precedence) · CPC title

• B23K11/315

  with one electrode moving on a linear path · CPC title

• B23K11/115 Primary

  by means of two electrodes placed opposite one another on both sides of the welded parts · CPC title