CA1063701A - Sequencing system for a blasting machine - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A sequencing system for a series of control circuits; each of which has its own control switch. A signal of spaced apart pulses is communicated simultaneously to all control switches.
Separate normally closed grounding switches are provided for all but the first of the series of control switches to make them inoperative. Each control circuit after the first is provided with a connection which opens its grounding switch in response to power flowing through the preceeding control circuit of the series.

Description

3637~

BACKGROUND OF THE INVENIIo The present invention relates to a sequencing circuit particularly adapted for use in blasting machines.
This application is a d~visional application of applicant's application Serial No. 192,277, filed February 12, 1974.
The pr~or art sequential blasting systems have suffered from the defect of not being able to set off a plurality of blasting charges at the precise time intervals of several milliseconds as is necessary to cause ground shock waves to be in phase. Applicants' Canadian Patent ~-1,028,20~ issued March 21, 1978, relates to a Blasting Machine which ~ill energize a plurality of blastlng ~ircuits at precisely spaced apart time intervals. The present invention is directed to safety means for preventing malfunctions Erom energizing the bla~ting circuits pre-maturely. To this end, the present invent~on provides a switching arrangement which isolates the triggering pulses from the electronic switches which cause energiza~ion of the individual blast~ing circuits. In addition, it i8 a feature of the present invention to provide additional switch means for grounding out each of the blasting circults until such time as the previously described switch means is closed. In this manner, two levels of safety protection are provided to make the blasting machine uniquely safe.
The invention relates to a sequencing circ~it comprising: generating means for generating space~ ap~rt electrical pulses, a plurality of conductors for communicating electrical energy to respective ènergy receiving elements, first means for energizing a first one of the conductors upon receiving an input signal, second means for energizing a second one of the conductors upon receiving an inpu~

signal, third means causing sequential electrical pulses of the generating means to sequentially operate the first mb/~ 2 -.

~ 1063701 and second means, and switch means which in one posltLon provides an open circuit between the generating means and the first and second means while grounding the conductors, and in another positlon closes the circuit between the generating means and the first and second means and opens ~he circuit between the conductors and ground.
In another aspect the invention relates to a sequencing circuit comprising first and second power distribution circuits each having a normally open control switch that is closed when its control element is energi~ed, a signal circuit having parallel branches connected to each control element of the first and second : ..
control swi~rhes, a normally closed shorting switch grounding out the control element of the second control switch when closed, and signal transfer means for opening the shorting switch after the first control switch is ~ ;
closed~
- The features of the present invention will become apparent to those skilled in the art to which the invention relates from ~he following description of the preferred `;
embodiments described with reEerence to the mb/p~ - 2a -: . . : - . , .

~0637~
accomp.lnying ~rawings forlnil1g a par~ of this specificatlo ancl in ~l1ich:
~igure l is a schematic wiring diagram of a DC
generator with controlled output voltage and having a battery power supply, and a pulse generator which produces pulses of predetermined duration that are spaced apart by selectable lengths of time; and Figure 2 is a schematic wiring diagram of one of a plurality of control circuits each of which are adapted to discharge a condenser to its output conductor upon receiving a pulse from the pulse generator, and each of which includes a grounding switch which normally shorts out the pulse transmitting circuitry to the following control circuit until the control circuit in question has discharged its condenser to its output conductor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Although the principles of the present invention may be otherwise embodied, they are herein shown and described as `
: : .
embodied in a blasting machine for setting off a plurality of ~
explosive charges at precisely spaced apart time intervals. ;
In order that the terminology used herein will be clearly understood, the term "switch" or ~Iswitch means" is used in a broad sense to indicate any type of electronic apparatus having a pair of power terminals and a control terminal that is connected to a control element or gate which when actuated al~ows energy to flow between the power terminals. Such switch means will include uni~unction transistors9 transistors, ~ i~
; silicon control rectifiers, etc....................................... `~
Because the blasting machine is to be used in remote areas, its primary source of power comprises two self-con-tained 7 l/2 volt batteries BTl and BT2 connected in series, with the negative terminal of BT2 connected to terminal 3 of 1 ;

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- ~637~
an eight t~rmin~l cclb]e socket Jl, which in ~urn ls colllmunicate~ l~y line 10 to tcrminal N of cable socket J2, whicll in turn is grourlded. The posltive ~erminal of ~Tl is connected ~o a ~use OL-l and then to terminal 1 oE socket Jl ;~
whose correspondi~lg plug Pl is jumpered to pin 2. The receiving terminal for pin 2 in socket Jl is connected by line 12 to the normally open mechanical switch SlA of a two element "Charge" switch Sl. The other terminal of SlA is connected to junction 14, whose purpose will later be described, and then to junctions 16 and 18. Junction 16 is connected to a terminal of the "Fire" switch S2A of a mechanical multiple ganged switch S2 and the other terminal is connected to the cen~er tap CT of the primary power winding of a power transformer Xl through resistor R5 and ~unctions 20 and 22. Junction 22 is connected to ground through condenser C4 to attenuate ripple~ Terminal Cl of the primary power winding is connected to the collector of an NPN transistor Ql and the emitter of Ql is connected to ground. The other terminal C2 of the primary power winding is connected to the collector of a NPN transistor Q2 whose emitter is connected to ground. Transistors Ql and Q2 are matching transistors, and a condenser Cl is connected between the collectors of the transistors for the usual reasons? as ~-is understood in the art. The transformer Xl also includes ;-a center tap control winding, the center tap CT of which is adapted to be supplied with voltage from the primary power -supply through junction 18, resistor R3, Zener diode Zl having a breakdown voltage of 6.8 volts, and junction 24.
Junction 24 is aIso connected to ground through resistor Rl 30 which is adapted to deactivate the control winding when the ,~
power supply is disconnected from the control windingO The terminal B2 of the control winding is connected to the base mb~-D 4 ~63701 of tran.si.stor Q2, cm~ h~ t~rm:Ln~:l 131 of the con~rol windLng i5 conn~cted to L11~ 1)as~ o~ tr~ng:Ls~or Ql. Because of the slight mismatch due to man~1Eac~ur:lng toler~lnces :Ln trans:istors Ql ~nd Q2, more current will Elow through one of the trans-istors than through the other when the power supply is connected to the transformer, and this will. start the transistors Ql and Q2 oscillating. The oscillation of the -primary power winding, will, of course, produce an oscillating current in the center taped secondary power winding of the transformer. The center tap of the secondary power winding ~:
is connected to ground 7 and the terminals Al and A2 of the secondary power winding are connected to diodes Dl and D2, respectively, to produce full wave rectification. The output .
from diodes Dl and D2 are connected to junction 26, and then through resistor R2, junction 28, and diode D3 to the high voltage bus 30. -`.
It is a feature of the present invention that the blasting machine is capable of properly setting off the . .
charges to which it is connected even though the voltage of the primary batteries has been depleted to lO volts... The ~ :~
equipment which is connected to the high voltage bus 30 is all designed to.operate on 90 volts even though the equipment so far described is capable of producing 120 volts, . ~ ~
It is a further feature of the present invention to i-prolong the life of the equipment connected to the high :~
voltage bus 30 by shutting off the power supply to the bus 30 whenever the voltage exceeds the nominal 90 volts that is required to satisfactorily operate the ci.rcuitry connected .i,~
to the high voltage bus 30. The voltage limiting function of ~
the present invention is very efficiently accomplished by the : .
voltage regulating circuitry which will now be described~ ~ :
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The volLa~e re~ulatillg circuitry comprises swltch Q3 wh:Lch is an NPN transistor, the collector of which is connected to the pr:imary power supp:Ly on the transformer side oE R3 through the llgh~ emittil~g diode LED-l. The emitter of switch Q3 is connected to ground through terminal 32 and resistor R6. The base or gate of the switch Q3 is connected to the junction 28 on the high voltage output of the transformer through junctions 34 and 36 and Zener diode Z2. Zener diode Z2 has a breakdown voltage of approx-imately 90 volts, and when the output voltage of the power transformer exceeds this voltage, positive voltage ls applied to the gate of Q3 to actuate the gate and ground out the control wi~ding of the ~ransformer through the light emitting diode LED-l. LED-l indicates that the necessary voltage has been reached in the equipment to satisfactorily operate all of the blasting circui~ry that is connected to . ;
the high voltage bus 30. Resistor R4 and condenser C3 communicates junctions 34 and 36 to ground to eliminate any :
high frequency that might otherwise be applied to the gate of transistor Q3~ A condenser C2 is placed between the junction 28 and ground to filter out ripple from the high voltage power supply. Diode D4 is connected between junction 20 of ~ :
the primary power supply and junction 28 of the high voltage power supply to give a nominal 15 volt boost to the bus 30, and thereby improve the efficiency, and reduce the length of time required to adequately charge the equipment connected to the high voltage bus 30.
The blasting machine of the present invention:further comprises and utilizes a timing circuit which generates pulses ~ .
of predetermined length which are separated by adjustable ~ :
periods of time to give a total cycle corresponding to the desired spacing between individual and sequential blasts or b C /(~

~(~63701 detonatlons. Tt is ~ furth~r Eeature of the presen~ inventlon to provide a "lockout" circuit fvr thc pulse generator whLch will prevent the c~ntrol pulses from being transmitted out of the gener~tor to the various blast initiating circuits.
This "lockout" circuit operates in con~unction with the voltage regulator circuit above described, and "locks out" the pulse generator until such time as the voltage on the bus 30 has reached the proper voltage for adequately operating the blast circuitry attached to and receiving its energy from the bus 30. The "lockout" circuitry comprises a switch Q4, which is shown as a silicon control rectifier, having its anode connected `
to the 15 volt power supply at junction 18 through resistor R9. The cathode of the switch Q4 is connected to ground, and the gate of Q4 is connected to the junction 32 that i9 supplied with the emitter current of Q3 and which in turn is connected to ground through resistor R6. When no current is flowing through the switch Q3, the gate of Q4 will be grounded and the switch Q4 will be nonconducting, so that the nominal 15 volts will exist at the anode of Q4. This nominal 15 volts is transmitted through conductor 38 and diode D6 to the gate, ;-or base, of "switch" Q7 of the pulse generating circui~ry which will later be described. The switch Q7 shown is a PNP
transistor, and the 15 volts which exlst in conductor 38 ~ :
when switch Q4 is nonconducting is transmitted to the base of Q7 to keep Q7 turned off. However, when Q4 is turned on by reason of the voltage having reached the necessary 90 volts to pass through Zener diode Z2, Q3 and Q4 are turned o~, and ~
the voltage at the anode of Q4 drops substantially to zero ; ;
due to electron flow through the silicon control rectifier Q4. Thereafter positive voltage can no longer be supplied through D6 to the gate of Q7 and this then allows the normal functioning of the pulse generator to take over 7 and supply bc/,Q~

;37~L
its c:ontrol slgnal to tllc g~te oE ~7. Switcll Q7 can then turn on, and opcrate in L~s norlnally inten~led manll~r as w-lll later be described. The "lockout" signal provided by the s~itch Q4, in con~unction with the dual function of the switch Q7, which normally operates as a pulse generating amplifier, performs a unique safety function, which prevents control signals from being transmitted'to the later described ~
individual blast c~rcuits before sufficient voltage is supplied ' to the individual blasting circuits to assure their proper '~
functioning.
The pulse generator of the present invention is also made to operate at a voltage which i5 less than that which is normally supplied, in order that it will be assured , of perfect operation even though a deterioration of the battery or circuit components has occurred., The pulse gen-erator is made to operate at a nominal 9 volts which is produced from the 15 volt power supply by bleed through resistor R27 connected to junction 14, and conductor 40 that is connected to Zener diode Z3 which is In turn connected to ground. Zener diode Z3 has a threshold voltage of 9~1 volts, so that any voltage above this value is bled to ground through the resistor R27. An adjustable amount of this voltage is obtained from the sliding contact 42 of a variable resistor R22 which is connected in series wit~ resistor R23 which in turn is grounded. The adjusted voltage from sliding contact ~ , 42 passes through fixed resistor R10 to a 12 contact switch 44 having resistors Rll through R21 respectively connected between respective contacts of the switch 44. A condenser C5 is connected between the sliding contact 42 and ground to take out ripple. The sliding contact 46 of the switch 44 is connected by conductor 48 to junction 50 which in turn is connected both to the control element of a switch Q6 and a ..

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: - .-: .. ,- :

;3701 storag~ conclcn~ser C61 the other side of which i5 grounded.
The val~le of R10 i9 selected so as ~o give a ]0 millisecond delay ln chclrging C6, a~d each of the resistors R7 through R21 have values to give an additional 10 milliseconds delay for each of the respective resistors, so that when the sliding contact 46 and all of the resistors including R 21 are used, a 120 millisecond delay is obtained.
Resistors R10 through R21 can also be changed to give other values of delay, if so dcsired.
Switch Q6 shown in the drawing is a unijunction transistor, and the gate thereof is the emitter. The breakdown, or the threshold voltage of the unijunction transistor is such that when the voltage on the condenser C6 exceeds this voltage, conduction occurs through the base of the unijunction transistor. Base 1 of Q6 is connect~d to ground through resistor R299 and the base 2 of ~6 is connected to junction 52 which is connected to the 9 volt power supply 40 through resistor R24. Conduction of-Q6 produces a negative pulse at junction 52 which is transmitted through condenser C7 to the gate of switch Q7 previously referred to. In the present instance switch Q7 is a PNP transistor, so that the negative pulse from Q6 will turn Q7 on to amplify the signal if D6 anode has been `
groundedJ as previously referred to, by reason of Q4 having been made conductive. Q4 is made conductive, as previously explained, when the voltage in the high voltage bus 30 is above approximately 90 volts. The side of condenser C7 opposite to that which receives the negative pulse from Q6 is connected to the 9 volt conductor 40 through a resistor R25. The emitter of Q7 is also connected to the positive 9 volt conductor 40 through a resistor R26, and the collector of Q7 is connected to ground through resistor _ g _ ~
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~63701 R30, junctio11 54 ~n~ resLstor R31. Refii~stors R25 a~ R26 are so selected ~Is to provide a negative polarity on the base or gatc o~ Q7 by reason of a pulse originating from Q6. Q7 amplifies this pulse, and ~his pulse is in turn conducted from Junction 54 to the gate or base of another switch Q8, ~hich in the present inventlon is an NPN
transistor. The emitter of Q8 is connected through Zener diode Z4 to ground, and the collector of Q8 is connected to the primary power supply ~unction 14 through resistor -R28. Zener diode Z4 is selected to maintain a back -~voltage of approximately 3.9 volts on the emitter of Q8 when it is conducting, so that a generally square wave shaped pulse is produced on the signal output conductor 56 from the pulse generator. Resistor R32 is connected between the output conductor 56 and ground to assure an immediate -drop in voltage after the pulse is transmitted. Signal output conductor 56 contains a second element S2B of the ~*-"Fire" switch S2 which is normally open to prevent the signal from being transmitted to the charge detonating circuits, later to be described, until such time as the "Fire" switch is depressed.
Socket Jl is used to provide a quick coupling for a battery charger, and for a circuit tester, which will not herein be described. Signal output conductor 56 is connected to terminal 6 of socket Jl. Terminal 5 of `;socket Jl is connected to a second element SlB of the - ganged-"Charge" switch, and pins 4 and 5 of plug Pl are interconnected to ground terminal 5 to terminal 4 through ground line lO. -It is a feature of the present invention that the blasting machine utilizes a control pulse generated by the charging and discharging of a single circuit, as opposed ' ':

bct '' ': -;'. ~-' ' ', ;
, . . . . .. . .
. . .

637()1 to a pluraLity of difrer~n~ circults, so that tllc spaclng b~twe~n con~rol pulses will be ~ubstantially identical and thus very ~cc-lrate. This control pulse is communlcated by signal output conductor 56 to a plurality (usually 10 or more) of substantially identical cap lgniting conductors, one of which 62 is shown in Figure 2 of the drawings.
Figure 2 of the drawings shows the first section (Section 1) of ten sec~ions, and section 1 is the first to receive the pulses from the pulse genera~or.
Once the "Charge" switch Sl has been depressed, and the light LED-l is lighted to indicate high voltage~ the "Fire" switch S2 is depressed. A train of pulses at a predetermined spacing is delivered to the signal output conductor 56, which train of pulses is delivered to an electronic control swi~ch 0101, which in the present '~
instance is ~he gate of a silicon control rectifier, through resistor R35 and diode D7. A stabilizing resistor R36 ;
is connected between the signal output conductor 56 and ~-ground to assure that the voltage will drop appreciably in the conductor 56 after each pulse is transmitted. The anode of Q101 is connected to the high voltage bus 30, through diode D101, and the cathode of Q101 is connected to ground through junction 60 and a one ohm resistor R102.
One side of a power storage or detonating condenser C101 having more than sufficient capacity to ignite a blasting ;~
cap is connected to the discharge of diode D101, while the - other side of the condenser C101 is connected to ground through resistor R103 and the normally closed switch S2C
of the "Fire" switch S2. A full 90 vol~s, therefore, is slowly accumulated on the condensor C101, and the corres-ponding condensers of the other nine blasting sections, - 11 - ': '.

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~0637~1 provL(Ie(l ~lla~ ~he "Charge" swLtch Sl has been depres~sed.
One of the ss~ety features of the pre~ent Invention is that the power storage condensers, and all o~ the other power condensers are prevented from accumulating a charge prior to the tlme that the "Charge" switch Sl is depressed.
This safety feature is accomplished by means of the normally closed switch element Sls which is connected to negative bus 58 and which in turn is communicated through a load resistor R33 to the individual blasting circuits. A diode Dl02 communlcates negative bus 58 to the positive ~erminal of ClOl to in effect short out the condenser ClOl through the load resistor R33 until such time as the "Charge" switch is depressed.
The resistor Rl03 on the negative side of the condenser ClOl is in tu~n connected by conductor 62 to the terminal A of the cable connector socket J2, and to which terminal ,-the line leading to the first of the series of caps that are to be detonated, is connected.
It will now be seen that the switch element S2C
provides the highly desirable safety feature of shorting ;
out the cap detonating line until such time as the "Fire"
switch is depressed. A resistor RlO4 is in parallel with the "Fire" switch element S2C to slowly dissipate - the charge on the condenser ClOl if for some reason an open circuit or very high resistance exists in the cap detonating circuit at the time that the "Fire" switch S2C is opened. The first pulse delivered to QlOl therefore allows electrons from the condenser ClOl to pass through the cap to ground and back through QlOl to the anode of condenser ClOl to dissipate the energy in the condenser and ignite the cap. This flow of current produces a positive voltage at the junction 60, which in turn is bc/~

-- ~06370~
pass~d tllrougll resistor R:L05 to th~ gate o~ a sLgnal transfer switcll Q102, wllich in ~he present instance is also a silicon control rectifier.
The catllode of Q102 is connected to ground and the anode of Q102 is connected through resistor R106 and resistor R107 to a 15 volt bus that is connected to the 15 volt power junction 18 through switch QS, which is ~-a PNP transistor. The base of Q5 is connected through resistor R8 and conductor 64 to terminal L of socket J2, and a plug, not shown, is used to jumper terminals L
and N to ground when a sequential operation of the blasting circuits is desired. Conductor 64, therefore, will normally bias Q5 "on", so that the 15 volts at terminal 18 is normally communicated to the anode of switch Q102. A resistor R7 is connected between the base of Q5 and the power terminal 18 to limit the bias that is delivered to the base of Q5 by the grounding of conductor 64. The positive 15 volt power supply from ~-resisto~ R107 is also comm~nicated through resistor R106, resistor R108 and resistor R109 to the gate of a shorting switch Q103, which is shown as an NPN transistor. The emitter of the transistor is communicated to ground, while the collector of the ~ransistor Q103 is connected through a diode D103 to the gate of a switch or silicon control rectifier Q201 of the second section, not shown, but which corresponds to Q101. The signals from the pulse generator are also transmitted from the signal output conductor 56 to the gate of the second stage switch Q201 through resistor Rlll, which corresponds in value to R35, -30 and the diode D103, which is similar to the diode D7.
A resistor RllO communicates the base of Q103 to ground so that a positive bias with respect to its emitter is '': ' bc/ ~b~-,, ,, , ,, , -10~i370~
normally mnintaine~l upon the sw:itch ~103 to short Ollt the s:ignal th~t is transmltted to the gate of the second section of cap igniting circuits until such time as C101 has properly fired.
As previously indicated, the firing of C101 .
produces a pulse on the gate of Q102 (if the current discharge by C101 has been greater than a predetermined value) which switches Q102 on. A light emitting diode ~' LED-101 is placed in parallel with resistor R106, ~o that when Q102 is turned on, the cathode of the light emitting diode LED 101 is grounded, and sufficient current flows through LED-101 to produee a light whieh indicates that C101 has been diseharged. A eondenser C102 is connected between the gate of Q102 and ground to produce a delay in the actuati.on of Q102 for such period of time as assures that an adequate eha.rge has been transmitted from C101 to the eap eireuit to ignite the eap. In addition to lighting LED-101, the actuation ~ ~
of Q102 grounds out the gate of Q103 9 whieh is normally ~ -"on", to turn Q103 off, so that the next pulse whieh is experienced in the signal output eonduetor 56 will ;~
no longer be shorted out and will in faet trigger the :~
eontrol gate of switeh Q201 of the immediately following seetion that is conneeted to signal output eonduetor 56. .:
A eondenser C103 communieates the junetion of resistors R108 and R109 to ground to provide a minimum delay for ;-the aetuation of Q103, whieh minimum delay is longer than .:
the pulse duration. This assures that the second seetion does not beeome triggered by the same pulse whieh triggered Q101. ;
With the exeeption of switch SlB, resistor R33, resistor R35, and diode D7, the remaining circuitry ~, ' - 14 - .

~0~;370~ ~
sllown in Fi~lre 2 will be exactly duplic~ted for each sec~ion that is connected to the signal OlltpUt conductor 56 other ~han the last section. The l~st section will be the same as the second section just described, excepting that no shorting out switch comparable to Q103 and accompanyLng circuitry corres ponding to R108, R109, RllO, Rll:L, condenser C103 and diode D103 is required.
As previously explained, the cap igniting conductor 1-0 62 for the first detonation section is connected to terminal A of the socket J2 of a cable connector, and terminals B through J of socket J2 are similarly connected to their respective detonating sections 2 through 10.
The plug P2 of the cable connector has its terminals A' through J' adapted to engage the respective terminals A through J of the socket J2 9 ancl has its terminals L' ... ,, . ,, - ~ .
and M' jumpered. When plug P2 is utilized, therefore, the base of Q5 is automatically grounded to turn Q5 "on", - ~ -to thereby assure sequential operation of the blas~
sections 1 through 10.
It will now be seen that the individual sections -~
of the cap firing circuitry effectively "cascadel' the control signal from the pulse generator from one section to another without the signal passing through the preceding section. In the present invention the control signal `
is transmitted si~ultaneously to all sections, but "lockout" means or "shorting" means are provided which disable the control signal on all downstream sections until the section immediately upstream to the section in question has successfully fired. It will further be seen that a mechanical firing switch is provided of a type which grounds out each individual cap firing conductor until such time as the "Fire" switch is actuated.
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~0637~
One o~ the eL~ments o~ the s~ln~e ~wit~ll dlsconrlects the control si~nal o~ pul~e gencrator frotn the cal) ~iring sections until the salDe "Fire" switch Is actuated. The "Charge" switch also has an elemen~ which grollnds out all of the firing condensers until such time as the 'lCh~rge" switch is actuated to charge the condensers immediately before firing. It will further be seen that the high voltage circuitry for the power transformer will have many applica~ions other than in blasting machines, as will the disabling circuit for disabling the pulse generator prior to the time that a proper voltage has been generated by the power transformer. The arrangement of using sequential signals from the pulse generator to sequentially turn on a plurality of sections of other circuitry also will have many applications other than in a blasting machine; and the individual sections and "cascading" arrangements will likewise have many applications other than in blasting machines.
While the invention has been described in consid~
erable detail, I do not wish to be limited to the particular embodiments shown and described, bu~ it is my intention to cover hereby all novel adaptations9 modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A sequencing circuit comprising: generating means for generating spaced apart electrical pulses, a plurality of conductors for communicating electrical energy to respective energy receiving elements, first means for energizing a first one of said conductors upon receiving an input signal, second means for ener-gizing a second one of said conductors upon receiving an input signal, third means causing sequential electrical pulses of said generating means to sequentially operate said first and second means, and switch means which in one position provides an open circuit between said generating means and said first and second means while grounding said conductors, and in another position closes said circuit between said generating means and said first and second means and opens the circuit between said conductors and ground.

2. A sequencing circuit comprising: generating means for generating spaced apart electrical pulses, a plurality of conductors for communicating electrical energy to respective energy receiving elements, first means for energizing a first one of said conductors upon receiving an input signal, second means for energizing a second one of said conductors upon receiving an input signal, third means causing sequential electrical pulses of said generating means to sequentially operate said first and second means, said first and second means comprising control switches and a bus which communicates the control terminal of said control switches to said signal generating means, and said third means comprising a shorting switch having power terminals and a control terminal with said power terminals communicating the control terminal of said second control switch to ground, fourth means for normally energizing the control terminal of said shorting switch to actuate said shorting switch, and fifth means actuated by a signal from a power terminal of said first control switch and supplying a signal to the control terminal of said shorting switch to bias said shorting switch off when said first control switch is actuated.

3. The sequencing circuit of claim 2 wherein said fifth means comprises: a signal transfer switch having a control terminal connected to a power terminal of said first control switch and a condenser between said control terminal of said signal transfer switch and ground to delay actuation of said signal transfer switch until a generally predetermined amount of energy has been transmitted by said first control switch.

4. The sequencing circuit of claim 3 wherein a power terminal of said signal transfer switch communicates with said fourth means to ground out the control element of said shorting switch and said circuit including another condenser communicating between ground and the control terminal of said shorting switch to delay deenergizing said shorting switch even though said signal transfer switch should be actuated while a pulse to said first control switch still exists.

5. A sequencing circuit comprising first and second power distribution circuits each having a normally open control switch that is closed when its control element is energized, a signal circuit having parallel branches connected to each control element of said first and second control switches, a normally closed shorting switch grounding out said control element of said second control switch when closed, and signal transfer means for opening said shorting switch after said first control switch is closed.

6. The sequencing circuit of claim 5 including means for delaying actuation of said signal transfer means for a period after said first control switch is closed to assure an actuating power flow in said first power distribution circuit.

7. The sequencing circuit of claim 5 including means for delivering spaced apart pulses of predetermined duration to said signal circuit, and means for delaying the signal to said shorting switch from said signal transfer means until after the pulse which initiated the action has become inoperative.

8. A cascade system for actuating a first and subse-quent plurality of power delivery circuits, comprising: first and subsequent series of electronic power switches in respective power delivery circuits and each having a control gate which when actuated closes its power delivery circuit, a signal circuit having branches each of which is connected to a respective control gate, said signal circuit being constructed to deliver spaced apart pulses of predetermined duration to said branch circuits simultaneously, a series of normal closed grounding switches respective ones of which are connected to a control gate of a respective one of said plurality of control gates to normally ground out the signal of the respective gate without attenuating the signal to said other branch circuits and first and subsequent series of signal transfer means the first of which opens the first of said series of grounding switches when said first power switch is closed, and the respective ones of said series of transfer means opening a subsequent one of said grounding switches when a preceding one of said series of power switches is closed.

9. The cascade system of claim 8 including first and subsequent series of time delay devices for respective ones of said first and subsequent series of signal transfer means, each time delay device delaying actuation of the shorting switch which it controls to assure an actuating power flow in the power des-tribution circuit from which it receives its signal.

10. The cascade system of claim 8 including first and subsequent series of time delay devices for respective ones of said first and subsequent series of signal transfer means for delaying opening of the grounding switch which it controls until the pulse to the power switch which controls the respective signal transfer means has terminated.