Method and apparatus for monitoring the wear on a rotary drill bit

Claim 2

In rotary drilling operations wherein a drill bit is driven by a rotary drive engine in continuous rotary movement and a varying amount of weight is placed on the bit, the method of continuously deriving a quantity indicative of the wear on the bit, comprising the steps of initiating a signal of preselected and fixed time duration for each preselected and fixed increment of rotary movement of the bit, continuously generating a pulse train having a pulse rate proportional to the weight on the bit; and counting said pulses only during each of said signal time durations, whereby the number of pulses registered by the counter during each such signal time duration is a measure of the product of the weight on the bit and one increment of rotary movement, and the total number of pulses registered by the counter during all such signal time durations is a measure of the sum of all such products, said sum of products being a quantity indicative of the wear on the bit.

Claim 3

The method according to claim 1, wherein said preselected and fixed increment of rotary movement of the bit is less than one complete revolution.

Claim 4

The method according to claim 2, wherein said pulse train comprises an A.C. signal, of which signal all excursions having a predetermined sign constitute the pulses of the train.

Claim 5

The method according to claim 3, wherein each said signal of preselected and fixed time duration is initiated by a time signal from an A.C. tachometer on the rotary drive engine, and said pulse train is derived from a weight transducer connected to the drilling line in combination with a D.C.-to-frequency converter.

Claim 6

In rotary drilling operations having a rotary drive engine, wherein the drill bit is in continuous rotary movement and a varying amount of weight is placed on the bit, apparatus for monitoring the wear on the bit comprising in combination means for generating a pulse train having a pulse ratE proportional to the weight on the bit, means for generating a gate signal having a predetermined time duration once for each predetermined constant increment of rotary movement on the bit, a gated pulse counter having two inputs and being adapted for counting said pulses during each of said gate signals, and circuit means for connecting said pulse train means to one of said counter inputs and for connecting said gate signal means to the other.

Claim 7

In rotary drilling operations having a rotary drive engine, wherein the drill bit is in continuous rotary movement and a varying amount of weight is placed on the bit, apparatus for monitoring the wear on the bit comprising in combination means for generating a pulse train having a pulse ratE proportional to the weight on the bit, means for generating a gate signal having a predetermined time duration once for each predetermined constant increment of rotary movement on the bit, a gated pulse counter having two inputs and being adapted for counting said pulses during each of said gate signals, and circuit means for connecting said pulse train means to one of said counter inputs and for connecting said gate signal means to the other.

Claim 8

The apparatus according to claim 5, wherein said predetermined constant increment of rotary movement of the bit is less than one complete revolution.

Claim 9

The apparatus according to claim 6, wherein said pulse train comprises an A.C. signal, of which signal all excursions having a predetermined sign constitute the pulses of the train.

Claim 10

The apparatus combination according to claim 7, further including an A.C. tachometer on said engine, and wherein each said gate signal of predetermined time duration is initiated by a time signal from said A.C. tachometer on the rotary drive engine, and said pulse train is derived from a weight transducer connected to the drilling line in combination with a D.C.-to-frequency converter.

Claim 11

In rotary drilling operations, wherein a drill bit is maintained in continuous rotary movement by an engine and said drill bit is suspended by a drilling line whereby it may be subjected to a varying amount of weight, and whereby a weight transducer is associated with said drilling line, the combination including means for monitoring the wear on the bit comprising means for deriving from said weight transducer connected to the drilling line an A.C. signal having a frequency of the order of tens of kilohertz and proportional to the weight on the bit, means for generating a gate signal having a predetermined time duration of at least 5 milliseconds once for each predetermined constant increment of rotary movement of the bit, said increment being a fraction of one complete revolution, and said gate signal being initiated by a time signal from an A.C. tachometer on the rotary drive engine; and a gated pulse counter for counting the exursions of said A.C. signal having a predetermined sign during each of said gate signals.

Claim 12

In rotary drilling operations, wherein a drill bit is maintained in continuous rotary movement by an engine and said drill bit is suspended by a drilling line whereby it may be subjected to a varying amount of weight, and whereby a weight transducer is associated with said drilling line, the combination including means for monitoring the wear on the bit comprising means for deriving from said weight transducer connected to the drilling line an A.C. signal having a frequency of the order of tens of kilohertz and proportional to the weight on the bit, means for generating a gate signal having a predetermined time duration of at least 5 milliseconds once for each predetermined constant increment of rotary movement of the bit, said increment being a fraction of one complete revolution, and said gate signal being initiated by a time signal from an A.C. tachometer on the rotary drive engine; and a gated pulse counter for counting the exursions of said A.C. signal having a predetermined sign during each of said gate signals.