Device for electrically heating surface structures such as roads, bridges, airport runways, walls, and the like

Claim 1

A DEVICE FOR ELECTRICALLY HEATING OBJECTS OF LARGE SURFACE AREA COMPRISING HEATING CONDUCTOR MEANS ARRANGED UNDER THE SURFACE TO BE HEATING CONDUCTOR GROUNDED, MEANS FOR SUPPLYING THE HEATING CONDUCTOR MEANS WITH A VOLTAGE EXCEEDING THE TOLERENCE OF HUMAN BEINGS AND ANIMALS, THE LATTER MEANS INCLUDING A VOLTAGE SUPPLY MEANS AND CURRENT FEEDS FROM THE SUPPLY MEANS TO THE CONDUCTOR MEANS AND AN ELECTRICAL SAFETY DEVICE FOR SELECTIVELY INTERRUPTING THE CONNECTION BETWEEN THE HEATING CONDUCTOR MEANS AND THE VOLTAGE SUPPLY MEANS IN THE EVENT OF ROUND LEAKAGE OR SHORT CIRCUIT OF THE HEATING CONDUCTOR MEANS, SAID SAFETY DEVICE COMPRISING SWITCH MEANS BETWEEN THE VOLTAGE SUPPLY MEANS AND THE HEATING CONDUCTOR MEANS, A CURRENT TRANSFORMER HAVING A PRIMARY WINDING INDUCTIVELY COUPLED TO THE PRIMARY A SECONDARY WINDING INDUCTIVELY COUPLED TO THE PRIMARY WINDING, SAID CURRENT TRANSFORMER HAVING ZERO OUTPUT WHEN THE VECTOR SUM OF THE CURRENT IN THE CURRENT FEEDS IS BALANCED AND EQUAL TO ZERO, AND A TRIP COIL OPERATIVELY COUPLED TO SAID SWITCH MEANS AND TO THE SECONDARY WINDING OF THE TRANSFORMER FOR OPENING THE SWITCH MEANS WHEN THE VECTOR SUM OF THE CURRENT SUPPLIED TO THE CONDUCTOR MEANS IS NOT EQUAL TO ZERO, SAID CONDUCTOR MEANS INCLUDING A PLURALITY OF HEATING CONDUCTORS EACH CONSITUATED BY A CONDUCTIVE CORE, AN INSULATIVE SHEATH ENCASING SAID CORE, A CONDUCTIVE COVERING ENCLOSING THE SHEATH AND CONNECTED DIRECTLY TO GROUND AND AN INSULATING SHEATH ON EACH CONDUCTOR ENCLOSING THE CONDUCTIVE CONVERING THEREON.

Claim 2

A DEVICE FOR ELECTRICALLY HEATING OBJECTS OF LARGE SURFACE AREA COMPRISING HEATING CONDUCTOR MEANS ARRANGED UNDER THE SURFACE TO BE HEATING CONDUCTOR GROUNDED, MEANS FOR SUPPLYING THE HEATING CONDUCTOR MEANS WITH A VOLTAGE EXCEEDING THE TOLERENCE OF HUMAN BEINGS AND ANIMALS, THE LATTER MEANS INCLUDING A VOLTAGE SUPPLY MEANS AND CURRENT FEEDS FROM THE SUPPLY MEANS TO THE CONDUCTOR MEANS AND AN ELECTRICAL SAFETY DEVICE FOR SELECTIVELY INTERRUPTING THE CONNECTION BETWEEN THE HEATING CONDUCTOR MEANS AND THE VOLTAGE SUPPLY MEANS IN THE EVENT OF ROUND LEAKAGE OR SHORT CIRCUIT OF THE HEATING CONDUCTOR MEANS, SAID SAFETY DEVICE COMPRISING SWITCH MEANS BETWEEN THE VOLTAGE SUPPLY MEANS AND THE HEATING CONDUCTOR MEANS, A CURRENT TRANSFORMER HAVING A PRIMARY WINDING INDUCTIVELY COUPLED TO THE PRIMARY A SECONDARY WINDING INDUCTIVELY COUPLED TO THE PRIMARY WINDING, SAID CURRENT TRANSFORMER HAVING ZERO OUTPUT WHEN THE VECTOR SUM OF THE CURRENT IN THE CURRENT FEEDS IS BALANCED AND EQUAL TO ZERO, AND A TRIP COIL OPERATIVELY COUPLED TO SAID SWITCH MEANS AND TO THE SECONDARY WINDING OF THE TRANSFORMER FOR OPENING THE SWITCH MEANS WHEN THE VECTOR SUM OF THE CURRENT SUPPLIED TO THE CONDUCTOR MEANS IS NOT EQUAL TO ZERO, SAID CONDUCTOR MEANS INCLUDING A PLURALITY OF HEATING CONDUCTORS EACH CONSITUATED BY A CONDUCTIVE CORE, AN INSULATIVE SHEATH ENCASING SAID CORE, A CONDUCTIVE COVERING ENCLOSING THE SHEATH AND CONNECTED DIRECTLY TO GROUND AND AN INSULATING SHEATH ON EACH CONDUCTOR ENCLOSING THE CONDUCTIVE CONVERING THEREON.