Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
  • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
  • H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B3/00—Blasting cartridges, i.e. case and explosive
  • F42B3/10—Initiators therefor
  • F42B3/18—Safety initiators resistant to premature firing by static electricity or stray currents
  • F42B3/182—Safety initiators resistant to premature firing by static electricity or stray currents having shunting means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42C—AMMUNITION FUZES; ARMING OR SAFETY MEANS THEREFOR
  • F42C11/00—Electric fuzes
  • F42C11/06—Electric fuzes with time delay by electric circuitry
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42C—AMMUNITION FUZES; ARMING OR SAFETY MEANS THEREFOR
  • F42C15/00—Arming-means in fuzes; Safety means for preventing premature detonation of fuzes or charges
  • F42C15/40—Arming-means in fuzes; Safety means for preventing premature detonation of fuzes or charges wherein the safety or arming action is effected electrically

Definitions

• This invention relates to protection circuitry for electrical components and, in particular, to the protection of electrical initiation elements for use with reactive material, e.g., in squibs, detonators, and the like.
• the clamping interval may be in the range of from about 1 microsecond to about 100 microseconds, or from about 10 microseconds to about 100 microseconds.
• the initiator device may comprise a uni- . polar clamping circuit and a unipolar timer circuits, or it may comprise a bipolar clamping circuit and a bipolar timer circuit.
• one or both of the electrical initiation element and the protective circuitry may be formed as integrated circuitry.
• the initiation element and protective circuitry may be mounted on a header comprising two electrical leads connected to the protec- tive circuitry, and the device may further comprise a shell mounted on the header and a charge of reactive material in the shell for initiation by the initiation element.
• Figure 1 is a schematic representation of unipolar active clamping circuitry with an electrical initiation element in accordance with this invention
• Figures 5, 6 and 7 are plots of current flowing through a resistive element in place of an electrical initiation element as described in the Example, from which the clamping intervals are evident.
• the protective circuitry therefore functions by diverting away from the initiation element, for a short time interval ("the clamping interval"), at least a portion of any input current above a minimum threshold supplied to the ini- tiation element. After the clamping interval, the input current is permitted to flow to the initiation element.
• the clamping interval is selected to be long enough to block a typical transient signal, but not so long that the reliability of the response of the initiation element to a bonafide initiation signal is significantly affected.
• the response of the initiation element to the initiation signal is delayed by the clamping interval, so the initiation signal must exceed the function time of the initiation element by at least as much as the clamping interval.
• the protective circuitry 12 comprises a timer portion 14 comprising a timer circuit and a clamping portion 16 comprising a clamping circuit, both of which are powered by an input signal received at nodes 10a and 10b.
• Bridge 10 receives initiation signals and, possibly, various undesired signals such as circuit transients, electrostatic discharge, etc., via nodes 10a and 10b.
• the clamping portion 16 is con- nected across bridge 10 in parallel thereto relative to nodes 10a and 10b. In effect, clamping portion 16 comprises a switch which, when closed, creates a circuit in parallel with bridge 10 that diverts away from bridge 10 a significant portion of any current generated by a potential across nodes 10a and 10b.
• the clamping portion 16 is responsive to the initial application of a potential across nodes 10a and 10b which, in the illustrated circuit, defines a potential across bridge 10. However, the operation of clamping portion 16 is controlled by timer portion 14, which disables the clamping portion 16 after a predetermined time interval (the clamping interval) by generating a release signal that causes the clamping circuit to release (i.e., stop clamping) the input signal. If a potential remains across nodes 10a and 10b after the clamping inter- val, any current generated thereby will then flow through bridge 10 and may cause bridge 10 to function.
• FIG. 2 A circuit diagram of the particular embodiment of the protective circuitry 12 of Figure 1 is provided in Figure 2.
• the timer circuit of timer portion 14 comprises an RC circuit (resistance Rl and capacitor CI) together with transistors Ql and Q2.
• the clamping circuit of clamping portion 16 comprises a shunt switch comprising a resistor R2 and transistors Q3, Q4 and Q5. The operation of such protective circuitry 12 is described in the Example below.
• the protective circuitry shown in Figure 2 is unipolar in nature, i.e., it will function only in response to a potential across nodes 10a and 10b of a particular polarity.
• Clamping portion 16' comprises two clamping circuits, each comprising a shunt switch that works in conjunction with a diode and which is designed to clamp signals of an opposite polarity from the other.
• Timer circuit 122a controls a clamping circuit in clamping portion 16' comprising a shunt switch 118a that works in conjunction with diode 120a.
• Timer circuit 122a, shunt switch 118a and diode 120a cooperate to provide an active clamping function across bridge 10 for a predete ⁇ rrined clamping interval in response to input signals of a particular polarity.
• timer circuit 122b controls a clamping circuit comprising a shunt switch 118b and diode 120b to provide the active clamping function in response to signals of an opposite polarity from those to which timer circuit 122a, etc., respond.
• FIG. 4 A circuit diagram of a particular clamping circuit according to the schematic of Figure 3 is provided in Figure 4.
• the circuitry of Figures 3 and 4 include a zener diode portion 124 that protects the bridge, the timer portion and the clamping portion from high power transients such as electrostatic discharges whose magnitudes and/or speed exceed the clamping ability and/or response time of the clamping circuit.
• the zener diode portion 124 comprises two zener diodes in series but in reverse bias orientation relative to each other across nodes lOa' and 10b'.
• a zener diode portion may also be employed in the unipolar embodiment of Figures 1 and 2 across nodes 10a and 10b, optionally with a suitably biased single diode.
• the circuits represented in Figures 2 and 4 can easily be reduced to practice substantially as shown using discrete circuit elements.
• the preferred embodiment of the clamping circuits and of the electrical initiation element with which they are used is in the form of a solid state integrated circuit die having a solid state initiation element (e.g., a semiconductor bridge (SCB), tungsten bridge, or the like) formed on a suitable substrate.
• SCB semiconductor bridge
• an SCB die comprises a non-conductive substrate on which the SCB and optional associated circuit elements are formed.
• FIG. 4A There is shown in Figure 4A an initiator comprising an electrical initiation element and associated protective circuitry in accordance with this invention.
• Initiator 30 comprises an SCB die 32 comprising a non-conductive substrate (e.g., sapphire) on which is formed a semi- conductor bridge initiation element and protective circuitry in accordance with this invention, using integrated circuit manufactirring technology.
• Die 32 is secured to a header 34 by a thin layer of epoxy 36. Header 34 and epoxy 36 are formed from non-conductive material.
• Input nodes for the protective circuitry and the semiconductor bridge are provided by metallized lands 38a and 38b on the die.
• Electrical leads 40 are mounted in header 34 and are connected to metallized lands 38a and 38b by lead wires 42a and 42b.
• a shell 44 containing a reactive material 46 is secured to header 34 such that reactive material 46 is in contact with the initiation element on die 32.
• the reactive material 46 may comprise an explosive charge, whereby upon the functioning of the semiconductor bridge, reactive material 46 will generate an explosive output from shell 44.
• reactive material 46 may comprise a pyrotechnic material that generates a pvrotechnical output.
• SCB Two 1 ⁇ , 1W, Wirewound in series (simulates a standard SCB)
• Transistors Ql - Q5 were bipolar junction transistors with a beta of about 75, preferably at least about 50. Transistor Q5 must be capable of handling large currents (e.g., about 1 ampere (A)) with a low V CE - Upon the application of a simulated input current transient, a voltage developed across R (SCB) (which is a nominal 2 ⁇ resistance) (For testing purposes, a resistor is used in place of an SCB or other electric initiation element.). Until capacitor CI charges sufficiently to activate transistor Ql, both transistors Ql and Q2 are held in the "off state. This allows current to flow through resistor R2, providing base drive to transistor Q3.
• SCB voltage developed across R
• the transistor Q3 collector current provides base drive to transistor Q4, which in turn provides base drive to transistor Q5, which shunts at least a portion of the input current away from resistor R(SCB)- [0025]
• the timer circuit operates by delaying the turn-on of transistor couple Q1/Q2 until capacitor CI has charged sufficiently to activate transistor Ql. At that point, transistor Ql turns on and provides base drive to transistor Q2.
• Transistor Q2 when on, effectively generates a release signal that clamps the base-emitter voltage of transistor Q3, which turns off transistors Q4 and Q5, allowing substantially all of the remaining input current to flow through resistor R (SCB Due to the large current gain, the collector-emitter saturation voltage V CE(SAT) of transistor Q3 should always be less than V CE(S A T) of transistor Q4, and, similarly, the base-emitter voltage V BE of transistor Q4 should always be less than V B E of transistor Q5. [0026] The circuit contains hysteresis when the clamp turns off. Once the capacitor CI voltage is large enough to turn on transistor couple Q1/Q2, the clamp begins to turn off.
• the clamping circuit will not function unless the input signal generates a current in R2 sufficient to activate transistor Q3.
• the timer circuit transistor couple Q1/Q2 will not turn on until the input voltage exceeds their combined V BE thresholds. In this example, this means that there will be a range of input currents between 0.5 A and 0.6A where the clamp will most likely turn on, but may not turn off.
• the protective circuitry is easily designed by one of ordinary skill in the art so that the thresholds are below the magnitude of expected transient signals capable of causing the inadvertent functioning of the initiation element.
• Test data for the breadboard circuit are shown in Table 1 for 50 microsecond current pulse. The input current is the current into the input nodes of the circuit and the bridge current is the current measured through resistor R( SCB )-

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Electronic Switches (AREA)
• Automotive Seat Belt Assembly (AREA)
• Emergency Protection Circuit Devices (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2003
  • 2003-07-21 EP EP03765830A patent/EP1540681A4/de not_active Withdrawn
  • 2003-07-21 KR KR1020057001304A patent/KR20050069973A/ko not_active Withdrawn
  • 2003-07-21 US US10/521,955 patent/US20060098380A1/en not_active Abandoned
  • 2003-07-21 AU AU2003254056A patent/AU2003254056A1/en not_active Abandoned
  • 2003-07-21 JP JP2004523205A patent/JP2005533991A/ja active Pending
  • 2003-07-21 WO PCT/US2003/022723 patent/WO2004010554A2/en not_active Ceased

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