Signal device for worn tire treads

Claim 1

SIGNALLING APPARATUS CAPABLE OF DIFFERENTIATING BETWEEN GOOD AND BAD TIRE TREADS COMPRISING A GROUND DEVICE ADAPTED TO BE LOCATED IN THE PATH OF TRAVEL OF A TIRE ON AN AUTOMOBILE, A SIGNALLING DEVICE, AND AN ELECTRICAL CIRCUIT CONNECTING SAID GROUND DEVICE AND SAID SIGNALLING DEVICE, SAID CIRCUIT COMPRISING A FIRST ELECTRICAL CONDUCTOR CONSTITUTED OF A WIRE ELECTRICALLY CONNECTED AT ONE END TO SAID SIGNALING DEVICE, AND A SECOND ELECTRICAL CONDUCTOR CONTAINED IN SAID GROUND DEVICE SO AS TO EXTEND ACROSS SUCH PATH OF TRAVEL OF AN AUTOMOBILE TIRE AND ELECTRICALLY CONNECTED TO SAID SIGNALLING DEVICE AND TO THE OTHER END OF SAID FIRST CONDUCTOR, SAID SECOND CONDUCTOR BEING COMPOSED OF A PLURALITY OF PORTIONS OF CONDUCTIVE MATERIAL EMBEDDED IN READILY COMPRESSIBLE, RESILIENT MATERIAL AND SAID PORTIONS HAVING A MAXIMUM DIMENSION LESS THAN THE WIDTH OF THE TREAD CAVITIES IN AN AUTOMOBILE TIRE, SAID PORTIONS OF CONDUCTIVE MATERIAL BEING CONSTRUCTED AND ARRANGED IN SAID RESILIENT MATERIAL TO TEND TO MODIFY THE ELECTRICAL CIRCUIT TO OPERATE SAID SIGNALLING DEVICE WHEN AN AUTOMOBILE TIRE HAVING A WORN TREAD PASSES TRANSVERSELY OVER SAID SECOND CONDUCTOR IN SAID GROUND DEVICE, AND SAID MATERIAL IN WHICH SAID PORTIONS OF CONDUCTIVE MATERIAL ARE EMBEDDED HAVING SUCH COMPRESSIBLENESS AND RESILIENCY THAT WHEN A GOOD TIRE PASSES TRANSVERSELY OVER SAID SECOND CONDUCTOR THOSE OF SAID PORTIONS OF CONDUCTIVE MATERIAL UNDERLYING THE TREAD CAVITIES IN THE GOOD TIRE WILL NOT HAVE SUFFICIENT PRESSURE EXERTED THEREON TO EFFECT SAID MODIFICATION OF THE ELECTRICAL CIRCUIT TO OPERATE SAID SIGNALLING DEVICE.