Apparatus for investigating earth formations

Claim 1

ACOUSTIC VELOCITY LOGGING APPARAUTS FOR INVESTIGATING EARTH FORMATIONS TRAVERSED BY A BOREHOLE COMPRISING: AN ELONGATED HOUSING ADAPTED FOR PASSAGE THROUGH A BOREHOLE; TRANSMITTER MEANS IN SAID HOUSING FOR GENERATING PULSES OF ACOUSTIC ENERGY; MEANS FOR REPETITIVELY ACTUATING SAID TRANSMITTER MEANS; AT LEAST FIRST AND SECOND RECEIVER MEANS IN SAID HOUSING SPACED FROM ONE ANOTHER AND IN ONE DIRECTION FROM SAID TRANSMITTER MEANS AND EACH RESPONSIVE TO PULSES OF ACOUSTIC ENERGY FOR DEVELOPING CORRESPONDING ELECTRICAL SIGNALS; FIRST AND SECOND PULSE GENERATING MEANS IN SAID HOUSING CONTINUOUSLY COUPLED RESPECTIVELY TO SAID FIRST AND SECOND RECEIVER MEANS, SAID FIRST PULSE GENERATING MEANS BEING TO SAID ACTUATING MEANS FOR RESPONSE TO ELECTRICAL SIGNALS FROM SAID FIRST RECEIVER MEANS AFTER A PREDETERMINED TIME DELAY FOLLOWING ACTUATION OF SAID TRANSMITTER MEANS AND JUST PRIOR TO THE EARLIEST ARRIVAL OF EACH ACOUSTIC PULSE THEREFROM TO DEVELOP FIRST SHARP PULSES MARKING THE TIMES OF SUCH ARRIVALS, GATE MEANS COUPLED BETWEEN SAID FIRST PULSE GENERATING MEANS AND SAID SECOND PULSE GENERATING MEANS, SAID GATE MEANS OPERATIVELY CONDITIONING SAID SECOND PULSE GENERATING MEANS FOR RESPONSE TO ELECTRICAL SIGNALS FROM SAID SECOND RECEIVER MEANS DURING A PREDETERMINED PERIOD FOLLOWING EACH OF SAID FIRST SHARP PULSES FOR GENERATING SECOND SHARP PULSES MARKING THE EARLIEST ARRIVAL OF THE CORRESPONDING ACOUSTIC PULSE AT SAID SECOND RECEIVER MEANS; AND MEANS IN SAID HOUSING COUPLED WITH SAID FIRST AND SECOND PULSE GENERATING MEANS AND RESPONSIVE TO SAID FIRST AND SECOND SHARP PULSES FOR DEVELOPING A SIGNAL OUTPUT WHICH VARIES AS A FUNCTION OF THE TIME INTERVAL BETWEEN THE EARLIEST ARRIVALS OF EACH GENERATED ACOUSTIC PULSE AT SAID FIRST AND SECOND RECEIVER MEANS.