GB2132041A - Energy-conserving detonator exploder - Google Patents

Abstract

In an exploder for toroid coupled detonators, storage capacitors 30 are charged by a battery 20 and then supply the energy for firing, energy remaining in the capacitors 30 after the firing being discharged via a circuit 8 and applied to recharge the battery 20. The recharge circuit 8 includes an inverter oscillator, a step-up transformer and a rectifier (Figure 2). <IMAGE>

Description

SPECIFICATION Exploder This invention relates to the initiation of explosives, particularly in connection with toroid coupled detonators.

Toroid coupled detonators provide a very conve nient means by which a large number of detonator's can be rapidly linked to an exploder. A particularly useful exploder arrangement is described in Euro pean Patent Application published under No 54402.

Such exploders are normally designed to utilise a battery as the power source, that being most convenient in quarries and mines where the explod er is likely to be used. When the exploder is prepared for operation the battery charges the main storage capacitors to the appropriate reference voltage.

These capacitors supply the energy for firing the detonators. After firing has been completed to ensure that there could be no accidental firing any residual energy in the storage capacitors is discharged to earth.

In coalmines where the firing pulse is limited to about 4.5 milliseconds we have discovered that only about ten percent of the energy stored in the storage capacitors is actually used for firing which, of course, means that most of the energy supplied by the battery is just discharged to earth. The present invention has been made in an attempt to recover some of this wasted energy.

According to the invention there is provided a device for initiation of explosions which comprises a battery, storage capacitance adapted to be charged by the battery for supplying energy upon firing of the device, and re-charge circuit through which the energy in the storage capacitance after firing is discharged and applied to re-charge the battery.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a block diagram of an exploder; and Figure 2 is a diagram of the re-charge circuit.

Referring to the drawings, the exploder is, in principle, similar to the exploder as disclosed in the aforesaid specification of European Patent Application No 54402 and will not, therefore, be described in detail.

When safety switch SF 1/2 is closed a battery check unit 2 senses the voltage of battery or series of batteries 20 which may be of the nickel-cadmium type. If the voltage is above a predetermined level a light emitting diode 22 "Battery OK" is changed from red to green. The sensing of adequate voltage level also, by interlock circuit 10, permits the impedence sensor 15 to measure the impedance of the firing circuit. The impedance sensor 15 produces an analogue reference voltage proportional to the impedance of the firing circuit which is used to set a reference on charge sensor circuit 6. At the same time the diode 24 "Impedance OK" changes from red to green.

When both diodes 22 and 24 are green a signal is fed through the logic circuit 10 to charge circuit 7 to permit the main storage capacitors 30 to charge to the reference voltage set in the sensor circuit 6.

When the capacitors 30 are charged to the aforesaid voltage a signal is fed to logic circuit 10 to cause the diode 26 "Ready" to flash green. The exploder is now readyforfiring.

When firing switch buttom 28 is pressed a logic '1' is fed through logic circuit 10 to contact delay trigger 11. The delay trigger provides a four millisecond delay to allow contact bounce of the firing switch to settle after which the four and a half millisecond timer is activiated to start a firing pulse via trigger amplifier 13 and shut-off circuit 32. Positive bias is now applied to feed back current transformer 34 and output transistors 36 to start to oscillate at a frequency fixed by the inductance of the firing circuit, swamp inductance 38 and series tuning capacitor 40. The swamp inductance 38 provides protection of the output circuit when only one detonator is in circuit or if the output of the exploder is shorted accidentally. This swamp inductor limits the frequency of operation to something less than 30 kilohertz.With a full load of detonators inserted, for example 100 detonators, 300 metres T4 shot firing cable, and 20 Metres 24 swg looping wire, the frequency of operation will be approximately 16 kilohertz.

The capacitor 42 in shut off circuit 32 provides a low impedance to A.C. during the firing pulse. Diode 44 shorts the base of one transistor 36 to 0 volts at the end of the firing pulse when the output of the trigger amplifier 13 goes to zero, this stopping oscillation of the output circuit. Resistor 46 provides correct D.C. bias for output transistors 36.

When the four and a half millisecond timer 12 reaches the end of its time period a signal is fed to end of pulse detector 5 which triggers the bistable circuit 8 to inhibit further firing.

The shot firers safety switch SF 1/2 is then opened and remaining energy on the storage capacitors 30 is fed to the batteries 20 via discharge circuit 8 which comprises a variable output inverter unit 50 which converts the energy to an A.C. voltage, steps up the voltage at transformers 54 and rectifies it at diode network 56. The circuit 8 re-charges the battery 20 with approximately 50% of energy, the rest of the energy being dissipated in dump resistor 52 and in circuit losses.

A logic re-set circuit 21 is provided which ensures that all logic circuitry is set to the same state when the exploder is switched on.

By recovering at least some of the energy from the storage capacitors that formerly was discarded the exploder can be used for a considerably greater number of detonations without having to be withdrawn from use while the battery is re-charged. The invention can significantly increase the utilisation of the exploder.

1. A device for initiation of explosions which comprises a battery, storage capacitance adapted to be charged by the battery for supplying energy upon firing of the device and a re-charge circuit through which the energy in the storage capacitance after

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Exploder This invention relates to the initiation of explosives, particularly in connection with toroid coupled detonators. Toroid coupled detonators provide a very conve nient means by which a large number of detonator's can be rapidly linked to an exploder. A particularly useful exploder arrangement is described in Euro pean Patent Application published under No 54402. Such exploders are normally designed to utilise a battery as the power source, that being most convenient in quarries and mines where the explod er is likely to be used. When the exploder is prepared for operation the battery charges the main storage capacitors to the appropriate reference voltage. These capacitors supply the energy for firing the detonators. After firing has been completed to ensure that there could be no accidental firing any residual energy in the storage capacitors is discharged to earth. In coalmines where the firing pulse is limited to about 4.5 milliseconds we have discovered that only about ten percent of the energy stored in the storage capacitors is actually used for firing which, of course, means that most of the energy supplied by the battery is just discharged to earth. The present invention has been made in an attempt to recover some of this wasted energy. According to the invention there is provided a device for initiation of explosions which comprises a battery, storage capacitance adapted to be charged by the battery for supplying energy upon firing of the device, and re-charge circuit through which the energy in the storage capacitance after firing is discharged and applied to re-charge the battery. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a block diagram of an exploder; and Figure 2 is a diagram of the re-charge circuit. Referring to the drawings, the exploder is, in principle, similar to the exploder as disclosed in the aforesaid specification of European Patent Application No 54402 and will not, therefore, be described in detail. When safety switch SF 1/2 is closed a battery check unit 2 senses the voltage of battery or series of batteries 20 which may be of the nickel-cadmium type. If the voltage is above a predetermined level a light emitting diode 22 "Battery OK" is changed from red to green. The sensing of adequate voltage level also, by interlock circuit 10, permits the impedence sensor 15 to measure the impedance of the firing circuit. The impedance sensor 15 produces an analogue reference voltage proportional to the impedance of the firing circuit which is used to set a reference on charge sensor circuit 6. At the same time the diode 24 "Impedance OK" changes from red to green. When both diodes 22 and 24 are green a signal is fed through the logic circuit 10 to charge circuit 7 to permit the main storage capacitors 30 to charge to the reference voltage set in the sensor circuit 6. When the capacitors 30 are charged to the aforesaid voltage a signal is fed to logic circuit 10 to cause the diode 26 "Ready" to flash green. The exploder is now readyforfiring. When firing switch buttom 28 is pressed a logic '1' is fed through logic circuit 10 to contact delay trigger 11. The delay trigger provides a four millisecond delay to allow contact bounce of the firing switch to settle after which the four and a half millisecond timer is activiated to start a firing pulse via trigger amplifier 13 and shut-off circuit 32. Positive bias is now applied to feed back current transformer 34 and output transistors 36 to start to oscillate at a frequency fixed by the inductance of the firing circuit, swamp inductance 38 and series tuning capacitor 40. The swamp inductance 38 provides protection of the output circuit when only one detonator is in circuit or if the output of the exploder is shorted accidentally. This swamp inductor limits the frequency of operation to something less than 30 kilohertz.With a full load of detonators inserted, for example 100 detonators, 300 metres T4 shot firing cable, and 20 Metres 24 swg looping wire, the frequency of operation will be approximately 16 kilohertz. The capacitor 42 in shut off circuit 32 provides a low impedance to A.C. during the firing pulse. Diode 44 shorts the base of one transistor 36 to 0 volts at the end of the firing pulse when the output of the trigger amplifier 13 goes to zero, this stopping oscillation of the output circuit. Resistor 46 provides correct D.C. bias for output transistors 36. When the four and a half millisecond timer 12 reaches the end of its time period a signal is fed to end of pulse detector 5 which triggers the bistable circuit 8 to inhibit further firing. The shot firers safety switch SF 1/2 is then opened and remaining energy on the storage capacitors 30 is fed to the batteries 20 via discharge circuit 8 which comprises a variable output inverter unit 50 which converts the energy to an A.C. voltage, steps up the voltage at transformers 54 and rectifies it at diode network 56. The circuit 8 re-charges the battery 20 with approximately 50% of energy, the rest of the energy being dissipated in dump resistor 52 and in circuit losses. A logic re-set circuit 21 is provided which ensures that all logic circuitry is set to the same state when the exploder is switched on. By recovering at least some of the energy from the storage capacitors that formerly was discarded the exploder can be used for a considerably greater number of detonations without having to be withdrawn from use while the battery is re-charged. The invention can significantly increase the utilisation of the exploder. CLAIMS

1. A device for initiation of explosions which comprises a battery, storage capacitance adapted to be charged by the battery for supplying energy upon firing of the device and a re-charge circuit through which the energy in the storage capacitance after firing is discharged and applied to re-charge the battery,

2. A device as claimed in Claim 1, wherein a timer is provided for limiting the time during which energy is supplied for firing and for initiating discharge of the capacitance to re-charge the battery.

3. A device as claimed in Claim 1 or Claim 2, wherein means are provided for sensing the battery voltage and for giving an indication that the sensed voltage is above a predetermined level.

4. A device as claimed in any preceding Claim, wherein means are provided for sensing the impedence of a firing circuit to which the device is connectable.

5. A device as claimed in Claims 3 and 4, wherein the means for sensing the impedence of the firing circuit is activated by the battery voltage sensing means.

6. A device as claimed in Claim 4 or Claim 5, wherein the impedence sensing means provides a control for the charge applied to the capacitance by the battery,

7. A device as claimed in any preceding Claim, wherein energy in the storage capacitance after firing is discharged through an inverter unit.

8. A device for initiation of explosions substantially as described herein with reference to the accompanying drawing.