US2313101A - Blasting machine - Google Patents

Description

J. STUART, 2D

BLASTINLE March 9, 1943.

MACHLNE Filed Jan. 10, 1940 JQSEPH STUAR T 31 has not been as desirable machine is at its .highest value.

. Patented Mar. 9, 1943 BLASTING MACHINE Joseph smart, 11, Wilmington, Del., assignor. to Hercules Powder Company, Wilmington, Del., acorporation of Delaware Application January 10, 1940, Serial No. 313,264

7 Claims.

This invention relates to an improved portable dynamo for supplying the necessary electrical energy for-firing a plurality of electric firing devices and more particularly to an improved blasting machine for firing electric blasting caps.

The blasting machines having a capacity in excess of ten caps are usually those of the push down type, that is, the dynamo is operated by a rack bar that turns a pinion gear on the armature shaft. Machines of this type are in general use for firing a plurality of caps and are furnished in such sizes that an operator may fire upto 30, 50 or 100 caps at one time. The industry has also been supplied with blasting ma chines operated by a hand crank and a series of gears, but, due to diificulti'es in obtaining maxi mum current output quickly, thistype machine as the "push down type.

While the push down type machine is the most satisfactory blastingmachine known to the art there are difiiculties-encountered in its operation. This type of machine is unsatisfactory in its operation because the amount of. current developed depends upon the force or speed with whichthe rack bar is operated. The current.

loss of labor and decrease in production.

The electrical energy generated by means of a push down blasting machine is usually delivered to the firing line upon the closing of a meat that time when the energy generated by the This theory and operation alway holdstrue but since the electrical energy is dependent upon the speed with which the armature rotates and the speed of rotation depends upon the operator, there may be delivered to the firing line electrical energy of widely different values. The energy developed by the handcrank machine will vary as much as the push down type due to difierent speeds of operation.

The firing or detonation of a modern electric blasting cap usually occurs within 0.01 second after the energy is applied to it, so that it is apparent that the effectiveness of the blasting depends on its operation immediately upon closure of the mechanical switch. Unfortunately,-the

- switch points are liable to become corroded or pitted and in some instances, it is observed that the switch does not close with positive action, but completes and opens the circuit many times before finally' closing, with the result that the effective energy delivered by the machine during the critical interval, is much reduced.

Numerous attempts have been made to overcome the deficiencies of the operators, and the effects of wear. Larger machines have been constructed, but the advantages are ofiset by increased welghtand cost. One of the most promising developments ha been the employment of relatively light and inexpensive electrical condensers, placed across the terminals of the generator.

However, in practice, the benefits of the condenser are partly nullified by the fact that the discharge of the condenser produces heavy arc"- ing at the switch points and shortens their life. The discharge also consumes power and the energy of the condenser, instead of aiding in firing the caps, is partly lost at the switch.

'It is the object of this invention to provide a dynamo whichcan deliyer electrical energy to the firing line only when the voltage has reached a predetermined value.

chanical switch which is positioned to be operated It is a further object of this" invention to provide a blasting machine for initiating electric firing devices which cannot deliver a current a a blasting machine in which the current output does not vary with the operation.

A 'still further object of this invention is to provide a. blasting machine having voltage con- -trol or regulator tube which prevents the delivery of any but a definite minimum current. a I Other and further objects of this invention will be obvious upon an understanding of the illustrative embodiments about to be described or will beindicated in the appended claims and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and de--,

scription and is shown in the accompanying drawing forming a part of the specification wherein;

Fig. 1' is a front elevation view, partly in section, of a preferred embodiment of the invention illustrating a push down" type blasting machine.

Fig. 2 is a side elevation view, partly in section, of an alternative embodiment; of this invention and consists of a hand crank blasting machine.

Figs. 3, 4, and indicate the various electric circuits which may be used in the embodiments shown in Figs. 1 and 2; and

Fig. 6 shows an alternative method of using the principle of this invention by substituting for the generator a source of current such as a battery or other electrical energy supply.

Described generally the energy supplying machines of my invention comprises a source of electrical energy such as a generator, battery or electrical power lines connected through a suitable circuit including a voltage control or regulator tube and contact terminals. To the terminals of th machine of my invention there will be connected 2. suitable number of electric firing devices and, upon proper operation of the generator or closing of switches, the electrical charge is fed into the generator or dynamo circuit including the voltage control or regulator tube which, upon building up to a predetermined value, will discharge into the firing line and cause the detonation or ignition of the firing devices.

Referring again to the drawing and more particularly to Figs. 1 and 2, there is shown a suitable casing I in which is mounted a voltage control or regulator tube 2. Also within casing I there is mounted a source of electric current such as the generator or dynamo 4. The armature of this generator 4 may be rotated by the rack bar 5 having handle 6 through gears 1 (Fig. 1) or by hand crank 9 through gears 10 (Fig. 2). In either case the generator 4 produces electrical energy and establishes a voltage potential across the electrodes of the voltage control tube 2. At a given voltage the voltage control tube 2 discharges through terminals or binding posts II to which may be attached any suitable number of firing devices.

Typical methods of electrically connecting the generators shown in Figs. 1 and 2, are shown in Figs. 3, 4, and 5.

In Fig. 3 a shunt wound generator is shown with one of its output terminals electrically connected directly to one of the binding posts or contact terminals II and with its other output terminal connected to the other binding post ll through the voltage control tube 2.

.It is to be noted that the generator circuit including thevoltage control tube 2 and the contact terminals H to which maybe connected a plurality of firing caps is permanentlyclosed through the output terminals of the generator thereby forming a fixed electrical circuit through the terminals. I

In Fig. 4 a compound wound generator is shown which has its output terminal connected to the binding posts H in the same manner as described above.

In the wiring diagram of Fig. 5, there is shown a condenser l2 across the terminals of the shimt wound generator, located between the generator and the tube, to cause the current to build up to the desired point and to increase the capacity of the blasting machine.

In addition to the use of the manually operated generators, the electrical energy needed for firing the firing devices may be supplied by a battery I such as is shown in Fig. 6 or other well known sources of electrical energy such as any suitable power line available at the blasting location. Thus, a high voltage, low current battery 14 may be connected through a switch I5 to the condenser l2 and voltage regulator tube 2. The battery may be of the type commonly known as a B battery, having a high internal resistance, which is designated by the resistance ii. If the battery were connected directly to the firing line by closing the switch, misfires would probably result, because the internal resistance of the battery would limit the current to a low value insufiicient to fire the electric blasting caps. However, when the condenser and regulator tube are used, upon closing the switch the condenser is charged, until the critical voltage of the regulator tube is reached. The regulator tube then automatically discharges the energy stored in the condenser into the firing line. By suitable choice of circuit constants a heavy current may be passed through the firing circuit, even though the battery which supplied the original energy is capabl of providing only a fraction of this current.

A preferred voltage control tube 2 may be of the type manufactured by Westinghouse and known as type KX-642. While this tube has three'electrodes only two'are utilized and accordingly only two electrodes are illustrated on the drawing. The tube is rated as follows:

Breakdown voltage A. C.-R. M. S.

volts 300-500 Maximum discharge current for 2 sec.

Maximum short circuit current at which tube will clear at first current zero:

At 230 volts amperes 10 At 115 volts do 15 Maximum overall length inches 5 Maximum diameter do The tube may be arranged to allow the passage of current of any predetermined voltage and thus by using a tube of the proper rating in the blasting machine of this invention, any desired number of firing devices may be fired. The tubes preferably are ratedto break down when sumcient current is applied to insure the firing of 50 electric blasting caps. It will be understood however that I may manufacture a blasting machine by using a tube which will break down under any specified breakdown voltage. Thus, I

have iound that I may, by using the proper tube, produce a blasting machine having any desired cap rating. r

, From the foregoing description it will be seen that the present invention provides a blasting machine which cannot discharge into the firing line unless sumclent current is available to fire all devices connected on the line. This eliminates all shots in which part or all of the caps fail to shoot due to lack of suificient current in the line. The use of the control tube insures proper operation of the machine and prevents the use of generators which are defective. It allows inexperienced operators to be eificient blasters because they can set ofi a series of blasting caps only when they operate the machine properly. It allows a closer calibration of machine capacity, and gives assurance each shot fired will be successful. The machines with regulator tubes also have the advantage of not requiring a mechanical switch and thus pitting of switch with the attending loss of power is no longer a factor. These advantages have not been obtainable with the blasting machines used heretofore and the machines of the present invention are, therefore, a definite improvement over the prior machines. The machine is rugged in construction and the tube incorporated therein is located in a manner which provides assurance that it will function perfectly even under the rough usage to which blasting machines may be subjected.

As various changes may be made in the form, construction, and arrangement of'the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that alli matter herein is to be interpreted as illustrative and not in a limiting sense.

What I claim and desire to protect by Letters Patent is:

1. In a blasting machine the combination of a manually operable dynamo. contact terminals adapted to receive a plurality of blasting caps in electrical contact therewith conductor elements forming a fixed circuit between said dynamo and said terminals whereby energy from said dynamo may be conducted instantaneously from said dynamo directly to said terminals, and a voltage control tube in said circuit adapted to permit the flow of said energy under a predetermined electrical potential.

2. In a blasting machine the combination of a manually operable dynamo, contact terminals adapted to receive a plurality of blasting caps in electrical contact therewith, conductor elements forming a circuit in fixed electrical contact with said dynamo and said terminals whereby energy from said dynamo may be conducted instantaneously from said dynamo directly to said terminals, and a voltage control tube in said circuit adapted to permit the flow of said energy under a predetermined electrical potential.

3. In a blasting machine the combination of a manually operable dynamo, contact terminals adapted to receive a plurality of blasting caps in electrical contact therewith, a circuit permanently connecting said dynamo with said terminals whereby energy from said dynamo may be conducted instantaneously from said dynamo directly to said terminals, and a voltage control tube in said. circuit adapted to permit the flow of said 'energy under a predetermined electrical potential. 4. In a blasting machine the combination of a manually operable dynamo, contact terminals adapted to receive a plurality of blasting caps in electrical contaot therewith, conductor elements forming a closed circuit through said dynamo and said terminals including a plurality of blasting caps, whereby energy from said dynamo may be conducted instantaneously from said dynamo directly to said terminals, and a voltage control tube in said circuit adapted to permit the flow of said energy under a predetermined electrical potential.

5. In a blasting machine the combination of a manually operable dynamo including a dynamo circuit,- contact terminals in said circuitadapted to receive a plurality of blasting caps in electrical contact therewith, and a voltage control tube in said dynamo circuit adapted to permit the flow of energy from said dynamo directly and instantaneously to said terminals at a predetermined electrical potential.

6. In the method of firing a plurality of electrical firing devices with a source of electrical energy which includes a manually operable dynamo, the step of directly subjecting an electrode of a voltage control tube to an electrical potential flowing directly from said dynamo to said electrode, and the step of permitting the instantaneous flow of said energy to said firing devices under a definite'predetermined voltage potential.

7. In a blasting machine, the combination of a manually operable dynamo including a dynamo circuit, contact terminals in said circuit adapted to receive a plurality of blasting caps in electrical contact therewith, and a switchin said cir cuit, said switch consisting of a gas-filled, cold cathode tube having a break-down voltage between about 300 and about 500 volts, and a current capacity of about 50 amperes for at least 2 seconds, said switch being adapted to automatically permit the flow of energy from said dynamo to said terminals at a predetermined electric potential.

. JOSEPH STUART, II.

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