Arc burn back preventive systems

Claim 1

IN ARC-WELDING APPARATUS OF THE TYPE FROM WHICH AN ELONGATED ELECTRODE IS FED TO BE PROJECTED ONTO A WORK ELECTRODE IN AN ARC MEANWHILE MAINTAINED BETWEEN THE ELECTRODES BY POWER SUPPLIED THERETO, THE COMBINATION OF AN ELECTRODE-DRIVING ASSEMBLY THROUGH WHICH SAID ELONGATED ELECTRODE NORMALLY EXTENDS TO BE DRIVEN THEREBY, SAID ASSEMBLY COMPRISING TWO PORTIONS WHICH OCCUPY ONE MUTUAL RELATIONSHIP WHEN SAID ELONGATED ELECTRODE EXTENDS, AND WHICH ASSUME A DIFFERENT MUTUAL RELATIONSHIP WHEN THAT ELECTRODE CEASES TO EXTEND, THROUGH THAT ASSEMBLY; AN ELECTRICAL SWITCH MECHANICALLY CONNECTED WITH AND OPERATED BY SAID ELECTRODE-DRIVING ASSEMBLY TO BE IN ONE ELECTRICAL CONDITION WHEN SAID PORTIONS OF THAT ASSEMBLY OCCUPY SAID ONE MUTUAL RELATIONSHIP AND TO BE OPERATED TO AN OPPOSITE ELECTRICAL CONDITION UPON THE ASSUMPTION BY SAID PORTIONS OF SAID DIFFERENT MUTUAL RELATIONSHIP; MEANS CONTACTING SAID ELONGATED ELECTRODE AND DISPOSED BETWEEN SAID ELECTRODE-DRIVING ASSEMBLY AND THE REGION OF THE ARC FOR SUPPLYING ARC-MAINTAINING POWER TO SAID ELONGATED ELECTRODE; AND MEANS, ELECTRICALLY CONNECTED WITH SAID SWITCH AND RESPONSIVE THERETO IN THE OPERATION THEREOF FROM SAID ONE TO SAID OPPOSITE ELECTRICAL CONDITION, FOR INTERRUPTING THE SUPPLY OF ARC-MAINTAINING POWER TO ONE OF THE ELECTRODES.