Acoustic well logging apparatus

Claim 1

WELL LOGGING APPARATUS FOR DETERMINING THE TRAVEL TIME OF ACOUSTIC WAVE ENERGY THROUGH TEH EARTH FORMATIONS TRAVERSED BY A BORE COMPRISING A LOGGING TOOL ADAPTED TO TRAVEL THROUGH THE BORE, SAID TOOL INCLUDING LONGITUDINALLY SPACED ACOUSTIC MEANS FOR PERIODICALLY GENERATING AND RECEIVING ACOUSTIC WAVE ENERGY, MEANS IN SAID TOOL RESPONSIVE TO ACOUSTIC WAVE ENERGY FOR DERIVING PAIRS OF ELECTRICAL SIGNALS IN WHICH SIGNALS OF EACH PAIR ARE SPACED A TIME DURATION APART REPRESENTATIVE OF THE TIME REQUIRED FOR ACOUSTIC WAVE ENERGY TO TRAVEL THROUGH THE EARTH FORMATIONS BETWEEN AT LEAST TWO OF SAID ACOUSTIC MEANS AT A PREDETERMINED SPACING, INTEGRATING MEANS COUPLED TO SAID SIGNAL DERIVING MEANS FOR OBTAINING INDICATIONS OF THE TOTAL TRAVEL TIME OF ACOUSTIC WVE ENERGY ALONG INTERVALS OF THE BORE, SAID INTEGRATING MEANS INCLUDING MEANS FOR PERIODICALLY GENERATING PULSES IN A PREDETERMINED MANNER AND MEANS FOR COUNTING SAID PULSES, SAID INTEGRATING MEANS BEING RESPONSIVE TO SAID PAIRS OF ELECTRICAL SIGNALS IN SUCH A MANNER THAT SAID COUNTING MEANS COUNTS SAID PULSES DURING THE TIME DURATION BETWEEN THE SIGNALS OF EACH OF SAID PAIRS, MEANS COUPLED TO SAID ACOUSTIC MEANS FOR CHANGING SAID PREDETERMINED SPACING, AND MEANS COUPLED TO SAID COUNTER MEANS FOR VARYING THE COUNTING RATE OF SAID COUNTER MEANS AS SAID PREDETERMINED SPACING IS CHANGED.