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Publication numberUS3721885 A
Publication typeGrant
Publication dateMar 20, 1973
Filing dateNov 23, 1971
Priority dateNov 23, 1971
Also published asCA949126A, CA949126A1
Publication numberUS 3721885 A, US 3721885A, US-A-3721885, US3721885 A, US3721885A
InventorsLinkroum I, Mc Keown J, Phinney E
Original AssigneeBendix Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Blasting machine with overvoltage and undervoltage protection for the energy storage capacitor
US 3721885 A
Abstract
An electrical system for firing an explosive bridge wire device or the like which includes a battery powered blocking oscillator to charge a storage capacitor, a circuit controlling the maximum energy to be contained in the storage capacitor, and a circuit that determines the minimum energy in the storage capacitor before the storage capacitor can be discharged into one or more explosive bridge wire devices or the like.
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Description  (OCR text may contain errors)

iliieili Sates Patent McKeown et al.

BLASTING MACHINE WITH OVERVOLTAGE AND UNDERVOLTAGE PROTECTION FOR THE ENERGY STORAGE CAPACITOR Inventors: James E. McKeown, Sdriey;rrlrving E. Linkroum, Hancock; Earl M. Phinney, Oneonta, all of N.Y.

Assignee: The 4Bendix Corporation, Southfield,

Mich.

Filed: Nov. 23, 1971 Appl. No.: 201,525

U.S. Cl. ..320/1, 307/108, 317/80, 331/1 l l Int. Cl. ..H03k 3/30, H02m 3/22 Field of Search ..320/1; 331/111; 317/80; 307/108 IHT 1451March 20, 1973 [56"] References Cited UNrrED STATES PATENTS Primary Examiner-Bernard Konick Assistant Examiner-Stuart Hecker Attorney- Raymond J. Eifler et al.

[5 7] ABSTRACT An electrical system for firing an explosive bridge wire device or the like which includes a battery powered blocking oscillator to charge a storage capacitor, a circuit controlling the maximum energy to be contained in the storage capacitor, and a circuit that determines the minimum energy in the storage capacitor before the storage capacitor can be discharged into one or more explosive bridge wire devices or the like.

8 Claims, 2 Drawing Figures PATENTEUMARzolS SHEET 2 UF 2 BLASTING MACHINE WITH O VERVOLTAGE AND UNDERVOLTAGE PROTECTION FOR THE ENERGY STORAGE CAPACITOR BACKGROUND OF THE INVENTION This invention relates to an improved blasting machine for detonating blasting caps or the like. The invention is more particularly related to a battery powered blasting machine of the capacitor discharge type.

Basically, electrical systems for firing explosive devices include a source of power such as a battery, an oscillator, a transformer responsive to the oscillator for stepping up the pulses therefrom, a storage capacitor which is charged by the pulses from the transformer, and a trigger circuit which allows the energy stored in the capacitor to discharge to fire an explosive device. The energy stored in the capacitor is discharged through the explosive device by means of a triggering circuit which may be operated automatically or manually. Examples of such blasting devices may be found in U.S. Pat. No. 3,417,306 entitled Regulated Voltage Capacitor Discharge Circuit to .l. L. Knak, issued Dec'. 17, 1968; and U.S. Pat. No. 3,275,884 entitled Electrical Apparatus for Generating Current Pulses to L. H. Segall et al., issued Sept. 27, 1966.

In certain blasting operations such as those performed in tunnels and shaft mining, it may be necessary to connect from as few as 1 blasting cap and as many as l50 blasting caps together in a parallel circuit. Parallel connections are used becausesuch connections permit rapid connection ofthe blasting caps with minimal possibility of error. To insure that all the blasting caps are fired, the blasting machine must always deliver a given minimum energy each time it is fired, otherwise all of the blasting caps may not be fired. Further, it is also important that the blasting machine does not deliver too much energy to the blasting caps, otherwise malfunction of some of the blasting caps may occur. Therefore, to insure that all blasting caps are fired, the blasting machine must always deliver an amount of energy in a predetermined energy range depending upon the number of blasting caps to be fired.

Further, all too frequently, under heavy loading conditions, existing charging circuits utilizing a transformer having a control winding (teritary) experience high frequency oscillations that affect the operation of the circuit and, therefore, the maximum power that can be transferred to the load. The high frequency oscillations occur because the amount of feedback to the control winding that turns OFF the switch transistor in series with the primary winding depends upon the voltage across the secondary winding in parallel with the storage capacitor. At low magnitudes of charge on the loads on the storage capacitor, the feedback to the control winding is frequently insufficient to overcome a positive bias on the switching transistor. Therefore, the switching transistor is OFF for very short intervals, hence high frequency oscillations occur.

SUMMARY OF THE INVENTION This invention provides an improved blasting machine that prevents low energy and high energy firing and is not susceptible to spurious oscillations in the charging circuit that adversely affects the operation of the machine. The invention is a blasting machine like.

In one embodiment of the invention, the blasting machine comprises: a capacitor; means for supplying electrical energy to the capacitor, said means for supplying electrical energy comprising a battery, a transformer having a secondary winding and a primary winding connected to the battery, a first diode means and the capacitor connected together in series across the secondary winding to store energy generated by the current flowing through the primary winding, a solid state switch oscillator connected to the battery and the transformer to periodically interrupt current flow from the battery through the primary winding, the oscillator including: a first transistor having collector and emitter terminals in series with the primary winding, 'the transistor having alternate conductive and nonconductive intervals to periodically interrupt the current flowing from the primary winding; a first voltage divider network connected across the first transistor and the primary winding, the first voltage divider network including second diode means connected to the junction between the primary winding and the first transistor to direct current from the winding in a predetermined manner; and a second voltage divider network connected across the battery, the second voltage divider network including a second transistor having alternate conductive and nonconductive intervals to respectively control the conductive and nonconductive intervals of the first transistor whereby the flow of current from the battery to the primary winding is periodically interrupted causing current to flow in an oscillatory manner through the primary winding; means for producing a plurality of electrical pulses when the capacitor has reached a first predetermined energy level; switching means for receiving the pulses, the switching means operable to permit the discharge of the capacitor only during the presence of the pulses, whereby the capacitor cannot be discharged below the predetermined energy level; and means for preventing the capacitor from exceeding a second predetermined energy level which is above the first predetermined energy level whereby the capacitor is prevented from reaching energy levels above the second predetermined energy level.

Accordingly, it is an object of this invention to provide a battery powered explosive ignition system that is not adversely affected by the number of devices which it detonates and which supplies energy to the devices that falls within a predetermined energy range.

It is another object of this invention to provide an improved blasting machine that is safe and reliable.

The above and other objects and features of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings and claims which form a part of i this specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a blasting machine that utilizes the principles of this invention.

FIG. 2 is a schematic diagram of a preferred embodiment of the circuitry for a blasting machine shown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, FIG. 1 illustrates a block diagram of a blasting machine which utilizes the principles of the invention. The basic portion of the system includes a power supply 1, an energy storage device 3, such as a capacitor for storing energy supplied by the power supply 1, a pulse generator for generating pulses when the energy in the capacitor has reached a predetermined energy level, and a firing circuit 6 which permits the discharge of the energy in the energy storage device 3 through the load 8 which are the blasting caps or the like, when the trigger portion 7 of the firing circuit 6 receives pulses from the generator 5.

The power supply 1 may be either a.c. or d.c. and include the necessary electrical components for charging an energy storage device such as a capacitor.

The energy storage device 3 is preferably a capacitor. The voltage regulator 2 may be used in electrical circuit relationship with the energy storage device 3 to assure that the energy stored in the energy storage device 33 does not exceed a predetermined voltage level. The energy storage circuit may include a switch that, in the ON position permits the energy storage device 3 to store energy, and in the OFF position allows the energy storage device 3 to discharge so that no energy remains in the energy storage device 3 when the blasting machine is not in use. The charge and discharge switch 9 may be either a single switch or multiple switches and may also be part of the firing circuit 6.

A voltage indicator 4 may be used in combination with the pulse generator 5 to produce either visual or audible signals when the pulse generator 5 is generating pulses.

The firing circuit 6 includes a trigger 7 which allows the energy storage device 3 to discharge into the load 8. The trigger 7 may be a gaseous conductor of the threeelectrode type wherein the trigger electrode upon receiving pulses from the pulse generator 5 allows the remaining two electrodes which are in series with the energy storage device 3 to conduct, thereby allowing the energy stored in the device 3 to discharge into the load 8. If it is desired that the blasting machine not be automatically triggered, a switch may be located in series with the pulse generator 5 so that when the voltage indicator 4 gives indication that pulses are present, manually operating the switch to close the contacts will cause the trigger to conduct and discharge the energy into the load.

FIG. 2 is a schematic diagram of a preferred embodiment ofa blasting machine that utilizes a battery and an oscillator to charge the storage capacitor which will be discharged to fire a blasting cap or other explosive bridge wire device or the like. The dotted lines outlining portions of the circuitry indicate the power supply l, the energy storage device 3, the voltage regulator circuit 2, the voltage indicator 4 associated with the pulse generator, the pulse generator circuit 5, and the firing circuit 6.

The power supply 1 in this embodiment includes a battery 140, a switch 9, a smoothing capacitor 130, and a transistorized oscillator circuit in combination with a step-up transformer 150, the output voltage of which is applied to the energy storage means 3. In operation, the power supply circuit 1 operates as follows:

A solid state switch oscillator is powered by a battery 140 or other direct current source. In one embodiment twelve one and one-half volt batteries were used, which, because of the internal resistance thereof, provided a voltage between l0 to l2 volts. Connected across the battery 140 is a capacitor 130 which, when charged, provides additional current to the oscillator. A transformer 150 has its primary winding 101 connected into the oscillator circuit and its secondary winding 151 connected to a storage capacitor 153 through a diode 152 to store the energy generated by the oscillator. The windings 101 and 151 of transformer 150 are inductively coupled and wound and disposed in the manner indicated by the dots.

The solid state switch oscillator operates to intermittently interrupt current flow from the battery 140 through the primary winding 101 of the transformer 150 and includes a first switching transistor 103, a first voltage divider network (110, 111, 112, 113), a second voltage divider network (121, 122, 123), and first diode means (102, 104, 106) connected between the first voltage divider network and the primary winding 101 of the transformer 150 to direct the flow of current to and from the primary winding 101. The oscillator circuit shown is capable of producing oscillations in the range of 800 to 2,000 Hz.

The first voltage divider network includes a diode 110 and a plurality of resistors 111, 112 and 113 connected together in series across the primary winding 101 of the transformer and the first transistor 103.

The diode means that directs the current from the primary winding 101 includes a first diode 102 connected by its anode terminal to the junction between the primary winding 101 and the first transistor 103. To permit current to flow from the primary winding 101 when transistor 103 is off, diodes 104 and 106 are connected in series with one anode terminal connected to the junction between the primary winding 101 and the first transistor 103 and one cathode terminal connected to the junction between the second transistor 1 l2 and the third transistor 113.

The second voltage divider network includes a transistor 121, a resistor 122, and a resistor 123 connected together in series across the battery 140. The base of the first transistor 121 is connected, for biasing purposes, to the junction between 'the diode 110 and resistor lll of the rst voltage divider network. The base of the first transistor 103 is connected to the junction between resistors 122 and 123 to supply a current to the base of transistor 103 when the transistor 121 is in the conductive state.

The secondary winding 151 of the transformer 150 is connected to a diode 152 and a capacitor 153. When the battery is l0 to l2 volts, the maximum charge that can be obtained on capacitor 153 is about 7,000 to 8,000 volts. However, voltages of this magnitude are not generally required in battery powered explosive ignition systems, therefore, an additional circuit (not shown) may be added to limit the voltage across the capacitor 153. The energy stored in the capacitor 153 is used for firing an explosive bridge wire device or the like.

In this embodiment, when a constant current source having an output voltage of about volts is used in lieu of the battery 140 and the capacitor 153 is a 100 microfarad capacitor, the capacitor 153 can be charged to 200 joules within l0 seconds and to 400 joules within seconds. Since batteries deteriorate with use, they are capable of achieving the initial charged'energy previously stated, but tests reveal that when they are used to charge the capacitor 153 to 400 joules three times a day for 2l days, it would take a maximum of 7l seconds of charge time to obtain 400 joules of energy at the capacitor 153. The minimum charge time at the end of this period to obtain 400 joules of energy at the capacitor 153 would be 49 seconds.

The energy storage means 3 includes a blocking diode 152 and storage capacitor 153 in circuit relationship with the secondary winding 151 of the transformer 150. The discharge resistor 154 allows the energy storage in capacitor 153 to be discharged when the switch 9 in the power supply l is in the OFF position.

The voltage regulator 2 which prevents the voltage on the capacitor 153from exceeding a predetermined value includes a two-electrode spark gap 160, a resistor 163, a capacitor 165, and a resistor 167. The function of the regulator circuit is to drain excessive energy of the storage capacitor 153 to prevent the storage capacitor from exceeding a predetermined upper energy limit. The spark gap 160 is a normally nonconducting device that conducts when the voltage across the device has reached a predetermined voltage. In'this instance, the breakdown voltage of the spark discharge device 160 is chosen to be the predetermined upper voltage limit desired across storage capacitor 153. ln operation, the voltage across the storage capacitor 153 appears across the spark gap 160. As the storage capacitor 153 is charged, the voltage `across the spark gap 160 increases until the breakdown voltage of the device is reached. Thespark gap 160 then breaks down and conducts current to charge capacitor 165. The current through the spark device 160 decreases as capacitor 165 becomes more fully charged. Eventually the current through the spark device 160 decreases to the point where it no longer will support an arc in the discharge device 160. The arc extinguishes and spark gap 160 ceases conduction. The charge on the capacitor 165 is then discharged through resistor 167. As capacitor 165 discharges, the voltage across the spark gap device 160 therefore increases, and if the voltage across the storage capacitor 153 is still greater than the breakdown voltage of the spark gap discharge device 160, the discharge device 160 again conducts and the cycle is repeated again. If desired, a neon indicator light could be used in combination with this circuit to give an indication when the voltage regulator is operating. The suggested method with respect to a voltage indicating device would be to place a neon indicator light and resistor across capacitor 165 which is responsive to the charging and discharging of capacitor 165.

The pulse generator circuit 5 includes a two-electrode spark discharge device 170, resistor 171, capacitor 177, resistor 173, and resistor 175. The voltage indicator light 4, such as a neon bulb, is in circuit relationship with resistor 173 and 175 and is responsive to the charging and discharging of capacitor 177. ln operation, the two-electrode spark discharge device 170 will remain in a nonconducting state as long as the voltage on the storage capacitor 153 is less than the breakdown voltage of the spark discharge device 170. When the voltage on the storage capacitor 153 exceeds the breakdown voltage of the discharge device 170, the device conducts allowing current to pass through resistor 1'71 to charge capacitor 177. As the voltage on the capacitor 177 increases, the voltage across the spark device decreases until the spark device 170 returns to the original nonconducting state. At this time, capacitor 177 then discharges through resistors 173 and 175 which further applies a voltage to the neon light 4 which gives an indication that this circuit is in operation. When the voltage across the spark discharge device 170 again rises to the breakdown potential of this device, conduction begins again and the cycle repeats itself. Each time capacitor 177'is charged, voltage is applied to neon indicator light 4 through the resistor divider network 173, 175. The neon indicator light 4 stays lit until the voltage across the light drops below the minimum sustaining voltage of the light 4. By this means, each time capacitor 177 is charged, there is a visible light pulse to signal the operator that the minimum voltage has been reached and the blasting i machine may be tired. With this circuit, when the minimum voltage across the capacitor 153 is reached and pulses are being generated by the pulse generator, pressing the firing switch 181 in the firing circuit 6 will cause the pulses to be transmitted to the firing circuit.

The firing circuit 6 includes a three-electrode spark gap discharge device, a step-up transformer for raising the voltage of the pulses received from the pulse generator 5 and applying them to the trigger electrode of the spark discharge device 180, and a firing switch 181 which permits the trigger pulses from the pulse generator 5 to be transmitted to the primary winding 185 of the step-up transformer. For further details concerning the particular type of three-electrode spark gap discharge device required for this circuit see U.S. Pat. Nos. 3,187,215 entitled Spark Gap Device" to l. E. Linkroum issued June l, 1965, and 3,229,146 entitled Spark Gap Device with a Control Electrode Intermediate the Main Electrodes" to l. E. Linkroum issued Jan. l l, l966. Inoperation, when the firing switch 181 is in the OFF position, no pulses are being supplied to the spark discharge gap 180 thereby preventing the firing of any blasting caps attached to the output terminals 190. Further, the tiring switch 181 in the OFF position is yet in combination with the power switch 9 l in the OFF position to place the discharge resistor 154 ditions are met, the output pulses of the pulse generator are transmitted to the primary winding 185 of the step-up transformer where the pulses are stepped up to a higher voltage and applied to the trigger electrode of the spark gap discharge device through resistor 183 thereby causing ionization within the spark gap discharge device and permitting current to flow through the two main electrodes which allows the energy storage capacitor 153 to discharge through the blasting caps connected to the output terminals 190. If it is desired to eliminate manual firing of the blasting caps and to have the blasting machine discharge the energy in the capacitor 153 automatically when it has reached a predetermined energy level, the firing switch 181 may be eliminated completely. ln this instance, as soon as voltage pulses are available from the pulse generator 5, the three-electrode spark discharge device 180 would be triggered to discharge the energy in the capacitor 153 through the blasting caps (not shown) connected to the terminals 190.

OPERATION Referring now to FIG. 2, the circuit operates as follows: When switch 9 is in the OFF position, resistor 154 removes the energy stored in capacitor 153. When switch 9 is closed, resistor 154 is removed from the circuit and current flows from the battery 140 through capacitor 130 and through transistor 121, resistor 122 and resistor 123. Accordingly, a voltage is applied across the voltage divider network containing transistor 121 and the voltage dividing network containing diode 110. Since there is a positive voltage applied across the emitter base circuit of the transistor 121, the transistor 121 conducts permitting a current to flow through resistors 122 and 123 and through lead 124 to the base of transistor 103 which is in the nonconducting state. When the current to the base of transistor 103 is sufficient, transistor 103 conducts (ON). When the transistor 103 conducts, current flows through the transformer primary winding 101 and transistor 103. With current flowing to ground through the primary winding 101, transistor 121 begins to return to the nonconductive (OFF) state as the base to emitter current of that transistor begins to decrease. Eventually transistor 121 becomes nonconductive, removing the necessary base current to transistor 103 which also becomes nonconductive (OFF). Once the transistor 131 turns OFF, the electrical energy stored in the primary winding 101 during the ON or conduction period of transistor 131 is removed as current leaves the primary winding 131 and flows through diodes 104, 106, 110 and resistors 111 and 112. This action also operates to back bias transistor 121 so that it remains in the nonconductive state. Further, since during this time the rate of change of current with respect to time (di/dt) becomes sharply negative the voltage induced across the secondary winding 151 for this period also reverses and the secondary winding 151 becomes a current source. Therefore, during the time d/dt is negative, most of the energy stored in the primary winding of the transformer is transferred to the secondary winding 151 in a manner that allows the diode 152 to conduct and to supply energy to the capacitor 153 and to supply energy to the capacitor 153 and to a load (not shown). Thus, electrical energy which is fed to the primary winding during the conducting period of transistor 103 is transferred to the capacitor 153 during the nonconducting period of transistor 103. The entire action is cyclic for as the energy is removed from the transformer the reverse bias on transistor 121 is removed allowing transistors 121 and 103 to turn ON and repeat the entire operation again. (About 800 to 2,000 Hz.)

As the energy stored in the capacitor reaches a predetermined level, the pulse generating circuit 5 begins generating trigger pulses. This occurs when the spark gap discharge device 170 reaches its breakdown potential. To assure that the energy stored in the capacitor is above the predetermined energy level but not in excess of a second and higher energy level, a voltage regulator circuit 2 is utilized. This eliminates excessive energy levels that cause adverse operation of the blasting machine.

Once the trigger pulses are present and the energy stored in the capacitor is within a preferred range depressing the firing switch 181 applies trigger pulses to transormers 182 which causes spark gap device 180 to conduct, thereby allowing the energy in capacitor 153 to discharge into the blasting caps (not shown) attached to the outputs 190 and detonate explosives.

ln one satisfactorily operable system, the blasting machine described in FIG. 2 was powered by 6 one and one-half volt D size batteries or one l2-volt Energizer battery No. S-121 and the circuit elements add the values or were of the types indicated below:

Capacitor 130 Capacitor Capacitor 177 3,300 microfarad, 30 Volts d.c. 0.45 to 0.61 microfarad SKV 0.008 to 0.0l2 microfarad, 3.5KV

400 microfarad 2.5KV

0.025 to 0.03 microfarad SKV Capacitor 153 Capacitor 187 Resistor 122 6.2 ohms, llW Resistor 123 33 ohms ll2W Resistor 111 100 ohms 2W Resistor 112 1,000 ohms, l/2W Resistor 113 Resistor 154 10K ohms l/2W 3K ohms 10W Resistor 167 20K ohms 20W (2 in series) Resistor 163 2 ohms 20W (2 in parallel) Resistor 175 0.33 megohms 2W Resistor 173 l.36 megohms 4W (2 in series) Resistor 171 500 ohms 10W Resistor 186 20 megohms 1W Resistor 183 1K ohms 5W Resistor 189 10K ohms 10W Transistor 121 Transistor 103 Diodes 0,102,104,106 Diode 152 Discharge Device 160 Type MJE 341 Type 2N3055 Beta 20-35 GE Al4F Motorola MR 995A 2,200 volts d.c. (breakdown) Bendix Corp. Sidney, N.Y. Part No. l0-374l05-2l 2,000 volts d.c. (breakdown) Bendix Corp. Sidney,N.Y. Part No. l0-37412l-l4 Discharge Device Transformer 150 Transformer 182 Switch 9 and 181 While a preferred embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that changes may be made to the invention as set forth in the appended claims, and in some cases, certain features of the invention may be used to advantage without corresponding use of other features. For example, different types of semi-conductors, or solid state control devices may be substituted for the types illustrated. Accordingly, it is intended that the illustrative and descriptive materials herein be used to illustrate the principles of the invention and not to limit the scope thereof.

Having described the invention, what is claimed is:

l. A blasting machine comprising:

means for storing electrical energy;

means for supplying electrical energy to said energy storage means, said means for supplying electrical energy comprising:

a source of electrical energy;

a transformer having a primary winding connected to said source and a secondary winding;

a first diode means and said electrical storage means connected together in series across said secondary winding to store energy generated by the current flowing throughsaid primary winding;

a solid state switch oscillator connected to said source and said transformer to periodically interrupt current flow from said source through said prim ary winding, said oscillator including:

a first transistor having collector and emitter terminals in series with said primary winding, said transistor having alternate conductive and 'nonconductive intervals to periodically interrupt the current flowing from said primary winding;

a first voltage divider network connected across said first transistor and said primary winding, said first voltage divider network including second diode means connected to the junction between said primary winding and said first transistor to direct current from said winding in a predetermined manner; and

a second voltage divider network connected across said source of electrical energy, said second voltage divider network including a second transistor having alternate conductive and nonconductive intervals to respectively control the conductive and nonconductive intervals of said first transistor whereby the flow of current from said source to said primary winding is periodically interrupted causing current to flow in an oscillatory manner through said primary winding.

means for producing a plurality of electrical pulses when said energy storage means has reached a first predetermined energy level;

switching means for receiving said pulses, said switching means operable to permit the discharge of said energy storage means only during the presence of said pulses, whereby said energy storage means cannot be discharged below said predetermined energy level; and

means for preventing said means for storing electrical energy from exceeding a second predetermined energy level which is above said first predetermined energy level whereby said energy storage means is prevented from reaching energy levels above said second predetermined energy level.

2. A blasting machine as described in claim 1 wherein said means for preventing said means for storing electrical energy from exceeding a second predeter mined voltage level includes an electrical circuit which comprises:

a gaseous conductor connected in series to a resistor and a capacitor, said capacitor connected in parallel with a second resistor, said electrical circuit connected across said means for storing electrical energy whereby when said means for storing elec trical energy reaches said second predetermined energy level, said gaseous conductor conducts to prevent said means for storing electrical energy from exceeding said second predetermined energy level.

3. The blasting machine as recited in claim l wherein the first voltage dividernetwork of said means for supplying electrical energy to said energy storage means comprises: .L

between said first transistor and said source of electrical energy.

4. A blasting machine as described in claim 3 wherein said means for preventing said means for storing electrical energy from exceeding a second predetermined voltage level includes an electrical circuit which comprises:

a gaseous conductor connected in series to a resistor and a capacitor, said capacitor connected in parallel with a second resistor, said electrical circuit connected across said means for storing electrical energy whereby when said means for storing electrical energy reaches said second predetermined energy level, said gaseous conductor conducts to prevent said means for storing electrical energy from exceeding said second predetermined energy level.

S. A blasting machine which comprises:

means for storing electrical energy;

means for supplying electrical energy to said energy storage means, said means for supplying electrical energy comprising:

a source of electrical energy;

a transformer having a primary winding connected to said source and a secondary winding;

a first diode means and said electrical energy storage means connected together in series across said secondary winding to store energy generated by the current flowing through said primary winding;

a solid state switch oscillator connected to said source and said transformer to periodically interrupt current flow from said source through said primary winding, said oscillator including:

a first transistor having collector and emitter terminals in series with said primary winding, said transistor having alternate conductive and nonconductive intervals to periodically interrupt the current flowing from said primary winding',

a first voltage divider network connected across said first transistor and said primary winding, said first voltage divider network including second diode means connected to the junction between said primary winding and said first transistor to direct current from said winding unidirectionally to said first voltage divider network; and

a second voltage divider network connected across said source of electrical energy, said second voltage divider network including a second transistor having alternate conductive and nonconductive intervals to respectively control the conductive and nonconductive intervals of said first transistor whereby the flow of current from said source to said primary winding is periodically interrupted causing current to flow in an oscillatory manner through said primary winding;

means for producing a plurality of electrical pulses when said energy storage means has reached a first predetermined energy level, said means for producing electrical pulses including a second normally nonconductive gaseous conductor which is rendered conductive when a predetermined voltage is applied thereto and a resistor capacitor circuit in series with said second gaseous conductor so that when said second gaseous conductor is rendered conductive, said capacitor lowers the voltage applied to said second gaseous conductor below said predetermined value and said second gaseous conductor is rendered nonconductive;

switching means for receiving said pulses, said switching means operable to permit the discharge of said energy storage means only during the presence of said pulses, whereby said energy storage means cannot be discharged below said predetermined energy level, said switching means including a first normally nonconductive gaseous conductor in circuit relationship with said pulse means, said first gaseous conductor being rendered conductive upon receiving said pulses, whereby when pulses from said pulse means are transmitted to said first gaseous conductor, said first gaseous conductor is rendered conductive to permit said storage means to discharge and a switch connected between said first gaseous and said pulse means, said switch operable in the ON position to permit passage of said pulses to said first gaseous conductor, whereby the energy storage means is discharged only when said switch is in the ON position and when said pulse means is producing pulses; and

means for preventing said means for storing electrical energy for exceeding a second predetermined energy level which is above said first predetermined energy level whereby said energy storage means is prevented from reaching energy levels above said second predetermined energy level.

6. A blasting machine as described in claim 5 wherein said means for preventing said means for storing electrical energ mined voltage leve comprises:

,from exceeding a secor.id predeterincludes an electrical circuit which a third gaseous conductor connected in series to a resistor and a capacitor, said capacitor connected in parallel with a second resistor, said electrical circuit connected across said means for storing electrical energy whereby when said means for storing electrical energy reaches said predetermined energy level, said third gaseous conductor conducts to prevent said means for storing electrical energy from exceeding said second predetermined energy level.

7. A blasting machine as recited in claim 5 wherein said first voltage divider network of said means for supplying electrical energy to said energy storage means comprises:

wherein said means for preventing said means for storing electrical energy from exceeding a second predetermined voltage level includes an electrical circuit which comprises:

a third gaseous conductor connected in series to a resistor and a capacitor, said capacitor connected in parallel with a second resistor, said electrical circuit connected across said means for storing electrical energy whereby when said means for storing electrical energy reaches said predetermined energy level, said third gaseous conductor conducts to prevent said means for storing electrical energy from exceeding said second predetermined energy level.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3805115 *May 7, 1973Apr 16, 1974Ohio Res Energy IncBlasting machine
US3846690 *Jul 11, 1973Nov 5, 1974Co Generale D ElectriciteDevice for charging an electric power storage element to a predetermined voltage
US3863126 *Nov 2, 1973Jan 28, 1975Comp Generale ElectriciteDevice for charging at a predetermined voltage, an element for storing electrical power
US3864616 *May 3, 1973Feb 4, 1975John C HiortdahlCoin-operated control circuit for selectively energizing a plurality of machines
US3892182 *Dec 10, 1973Jul 1, 1975Cbf Systems IncSquib control circuit
US3898588 *Jun 19, 1973Aug 5, 1975Bofors AbDiode laser pumping
US3964395 *Oct 11, 1972Jun 22, 1976Gebruder Junghans GmbhElectrical primer for projectiles
US4047482 *Oct 14, 1975Sep 13, 1977Etat FrancaisElectronic igniter circuit for detonating an electric primer
US4119903 *Jan 5, 1978Oct 10, 1978Hewlett-Packard CompanyDefibrillator charging circuit
US4135219 *Jul 20, 1977Jan 16, 1979Tdk Electronics Co., Ltd.Demagnetizer for a magnetic head of a recording-reproducing device
US4157069 *May 13, 1977Jun 5, 1979Nitro Nobel AbInitiation of blasting detonators
Classifications
U.S. Classification361/251, 331/111, 307/108, 331/112, 102/219
International ClassificationH03K3/00, H02M3/338, H03K3/53, H02M3/24
Cooperative ClassificationH02M3/3381, H03K3/53
European ClassificationH03K3/53, H02M3/338A
Legal Events
DateCodeEventDescription
Sep 25, 1989ASAssignment
Owner name: UNISON INDUSTRIES LIMITED PARTNERSHIP, 530 BLACKHA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:IGNITION PRODUCTS CORPORATION;REEL/FRAME:005164/0245
Effective date: 19890106
Jan 13, 1989ASAssignment
Owner name: HOUSEHOLD COMMERCIAL FINANCIAL SERVICES, INC.
Free format text: SECURITY INTEREST;ASSIGNOR:UNISON INDUSTRIES LIMITED PARTNERSHIP;REEL/FRAME:005012/0090
Effective date: 19890106
Owner name: IGNITION PRODUCTS CORPORATION
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ALLIED-SIGNAL INC.;REEL/FRAME:005012/0079
Effective date: 19881231