Flexible detonator system

• US 7,146,912 B2
• Filed: 01/04/2005
• Issued: 12/12/2006
• Est. Priority Date: 12/07/1999
• Status: Expired due to Term

• Current Assignee: Detnet South Africa (Pty) Ltd
• Original Assignee: Dyno Nobel Sweden AB (Orica Limited)
• Inventors: Jönsson, Elof, Westberg, Jan
• Primary Examiner(s): Carone, Michael J.
• Assistant Examiner(s): Bergin, James S.
• Application Number:
  US11/027,975
• Publication Number:
  US 20050183608A1
• Time in Patent Office: 707 Days
• Field of Search: 102/206, 102/215, 102/217, 102/218, 102/264, 102/276, 361/248, 361/249
• US Class Current: 102/215
• CPC Class Codes: F42C 11/06 with time delay by electric circuitry
• CPC Class Codes: F42D 1/05 Electric circuits for blasting
• CPC Class Codes: F42D 1/055 specially adapted for firing multiple charges with a time delay
• CPC Class Codes: F42D 3/04 for rock blasting

Abstract

An electronic detonator system includes a control unit, a plurality of electronic detonators and a bus which connects the detonators to the control unit. Each electronic detonator includes a number of flags which may assume either of two possible values, each flag indicating a substrate of the respective detonators. The flags are readable from the control unit by means of digital data packets and the control unit is adapted, by means of these flags, to check the state of the electronic detonator and control the operation of the electronic detonator. When reading the flags, the electronic detonators give responses in the form of analog response pulses on the bus. The detonator system also includes a portable message receiver which on the basis of the flags obtains messages regarding the connecting status of a detonator.

Claims

1. A method for calibrating delay time in connection with firing an electronic detonator included in an electronic detonator system, in which an internal clock frequency in the electronic detonator is used when effecting the delay time and is calibrated in relation to an external clock frequency of a control unit, comprising in the electronic detonator the steps of:

extracting information about the external clock frequency from a digital data packet which is sent by the control unit to the electronic detonator,

comparing the external clock frequency which is extracted from the digital data packet with the internal clock frequency of the electronic detonator in order to obtain a ratio of the external clock frequency to the internal clock frequency,

using said ratio for calibration of the internal clock, and

setting a first flag in the electronic detonator after completed calibration, the flag indicating that at least one calibration has been carried out and the flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said flag.

2. A method as claimed in claim 1, wherein the step of comparing the external clock frequency with the internal clock frequency comprises the steps of:

extracting external clock pulses from a digital data packet, each bit in the data packet corresponding to an external clock pulse,

counting a predetermined number of external clock pulses by incrementing a first counter in the electronic detonator,

counting simultaneously with the preceding step a number of internal clock pulses by incrementing a second counter in the electronic detonator, and

comparing the external clock frequency with the internal clock frequency by comparing the numbers of pulses counted by the first and the second counter, respectively,

whereby a said ratio of the external clock frequency to the internal clock frequency is obtained.

3. A method as claimed in claim 2 which also comprises the steps of:

receiving a signal in an electronic detonator, the signal comprising a delay time which is expressed in a general time format,

storing said delay time in the detonator,

determining a correction factor in the detonator on the basis of the ratio of the counted number of external clock pulses to the counted number of internal clock pulses, respectively,

applying, In the detonator, said correction factor to the stored delay time In order to obtain an internal number of pulses which represents the number of internal clock cycles that corresponds to the delay time expressed in the general time format, and

storing the internal number of pulses in the detonator,

the thus stored, internal number of pulses representing the number of clock cycles which corresponds to the delay time received in the general time format.

4. A method as claimed in claim 3, further comprising the steps of:

before calibration setting a second flag in the electronic detonator, the second flag indicating that calibration is permitted in said detonator and the second flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said second flag, and

setting a third flag in the electronic detonator as soon as said counting of clock pulses has been initiated, the third flag indicating that calibration of the electronic detonator at issue is in progress in parallel with other signalling and other events in the electronic detonator system and the third flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said third flag.

5. A method as claimed in claim 2, further comprising the steps of:

before calibration setting a second flag in the electronic detonator, the second flag indicating that calibration is permitted in said detonator and the second flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said second flag, and

setting a third flag in the electronic detonator as soon as said counting of clock pulses has been initiated, the third flag indicating that calibration of the electronic detonator at issue is in progress in parallel with other signalling and other events in the electronic detonator system and the third flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said third flag.

6. A method as claimed in claim 1 which also comprises the steps of

receiving a signal in an electronic detonator, the signal comprising a delay time which is expressed in a general time format,

storing said delay time in the detonator,

determining a correction factor in the detonator on the basis of the ratio of a counted number of external clock cycles to a counted number of internal clock cycles, respectively,

applying, in the detonator, said correction factor to the stored delay time in order to obtain an internal number of pulses which represents the number of internal clock cycles that corresponds to the delay time expressed in the general time format, and

storing the internal number of pulses in the detonator,

the thus stored, internal number of pulses representing the number of clock cycles which corresponds to the delay time received in the general time format.

7. A method as claimed in claim 6, further comprising the steps of:

before calibration setting a second flag in the electronic detonator, the second flag indicating that calibration is permitted in said detonator and the second flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said second flag, and

setting a third flag in the electronic detonator as soon as said counting of clock pulses has been initiated, the third flag indicating that calibration of the electronic detonator at issue is in progress in parallel with other signalling and other events in the electronic detonator system and the third flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said third flag.

8. A method as claimed in 1, further comprising the steps of:

before calibration setting a second flag in the electronic detonator, the second flag indicating that calibration is permitted in said detonator and the second flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said second flag, and

setting a third flag in the electronic detonator as soon as said comparing of clock frequencies has been initiated, the third flag indicating that calibration of the electronic detonator at issue is in progress in parallel with other signalling and other events in the electronic detonator system and the third flag being readable from the control unit by means of a digital data packet comprising a question regarding the state of said third flag.