US2935303A

US2935303A - Thermal rock piercing control apparatus

Info

Publication number: US2935303A
Application number: US634219A
Authority: US
Inventors: Stanley H Royer; Alfred J Miller; Joseph J Calaman
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1957-01-15
Filing date: 1957-01-15
Publication date: 1960-05-03
Anticipated expiration: 1977-05-03

Description

1960 s. H. ROYER EI'AL 2,935,303

THERMAL ROCK PIERCING CONTROL APPARATUS Filed Jan. 15, 1957 2 Sheets-Sheet 1 Automatic compensator Confrol ONFF AUT. MAN. ir y Aufcmafic Biowpipe Conrrol I r )2: A.C.

INVENTORS STANLEY H. ROYER ALFRED J. MILLER JOSEPH J. CALAMAN A 7' TORN May 3, 1960 s. H. ROYER ErAL 2,935,303

THERMAL ROCK PIERCING CONTROL APPARATUS Filed Jan. 15, 1957 2 Sheets-Sheet 2 85x E FOE a E 5 a .F E i firzzo s A g a a E. E. 252

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INVENTORS STANLEY H. ROYER ALFRED J. MILLER JOSEPH J. CALAMAN BY mu ,3 '3

/7 Arr o A/ar muum on mm 5:; wuwodv United States Patent THERMAL ROCK PIERCING CONTROL APPARATUS Stanley H. Boyer, Elizabeth, and Alfred J. Miller, Westfield, N.J., and Joseph J. Calamari, Aurora, Minn assignors to Union Carbide Corporation, a corporation of New York Application January 15, 1957, Serial No. 634,219

6 Claims. (Cl. 255-46) The present invention relates to a thermal rock piercing apparatus of the type wherein a heating device, such as a blowpipe, is employed for directing heating against a body of rock to remove material therefrom and form a hole. More particularly, the apparatus of the invention includes an automatic control system for piercing deep blasting holes without requiring the constant attention of an operator.

The thermal piercing of blasting holes in bodies of rock, such as taconite iron ore, quartzite, traprock, granite and dolomite has been successfully practiced for a number of years with a heating device such as an oxy-fuel blowpipe, and has been described in the patent and other literature. For example, such a process has been described in detail in United States Reissue Patent Re. 22,964. The piercing of holes with a flame discharged from a blowpipe will be described hereinafter as exemplary of the invention but it is to be understood that the principles of the invention also apply to the piercing of holes with other heating devices.

The rate at which rock can be pierced with a heating device, such as an oXy-fuel flame is dependent upon the spallability of the rock itself. Since all rock is not homogeneous in structure, there is a variation in the speed with which a given body of rock can be pierced. It follows that if the rock has a relatively fast spalling rate, a faster piercing rate can be employed than that which can be used for rock having a slow spalling rate. Inefiicient operating conditions arise when the correct piercing rate corresponding to the pierceability (which is directed proportional to the spallability) is not properly maintained. For example, if the spalling rate is fast and the piercing rate is too slow, the tendency would be for the bottom of the hole to run too far ahead of the blowpipe tip. n the other hand, if the spalling rate is slow and the piercing rate is fast, the blowpipe tip would tend to run too close to the bottom of the hole. Both of these cases represent inefficient operation from the standpoint of piercing rate versus pierceability of the rock.

Since the pierceability of the rock varies, prior operation is dependent upon the skill of the operator. Some operators are very adept in determining the correct ratio between piercing rate and the distance between the blowpipe tip and the bottom of the hole. It is this distance that directly affects the efliciency at which one operates. It has been determined that, for a given rock, a specific and ascertainable distance between the blowpipe tip and the bottom of the hole yields the best results. For many typesof rock'their optimum distance has been found to be about 3 to 4 inches.

Manual operation of the blowpipe feed gives the operator complete responsibility for advancing and retracting the blowpipe as he sees fit. Retraction of the correct amount is dependent upon his skill and, since the operator cannot see the bottom of the hole, continuously maintaining the blowpipe at the optimum distance above the bottom of the hole will be extremely diflicult.

Heretofore, automatic control apparatus has been provided for thermal rock piercing blowpipes and such apparatus is described and claimed in Unite States Patent 2,679,381, issued May 25, 1954, to S. H. Royer et al. This apparatus, while it did provide means for arresting the advance of a blowpipe encountering an obstruction in normal advancement, does not provide means for maintaining an optimum distance between the blowpipe and the bottom of the hole.

It is, therefore, the main object of the invention to provide means for maintaining a rock piercing heating device at approximately an optimum predetermined distance from the bottom of the hole during the piercing operation when superimposed on a device equivalent to that of the above-mentioned US. Patent 2,679,381.

Other aims and advantages of the invention will be apparent from the following description and appended claims.

In accordance with the present invention, apparatus is provided for maintaining a mineral piercing device, such as a motor-driven, cable-suspended, rock-piercing heating device, at approximately an optimum predetermined distance from the bottom of the hole being pierced comprising, in combination, control means actuating the motor drive means for varying the rate of feed of the drive motor means; electric circuit means for periodically actuating the drive motor means to cause the heating device to rapidly advance to contact the bottom of the hole, electric timing circuit means responsive to the time required for the heating device to rapidly advance to contact the bottom of the hole, means for retracting the heating device a predetermined distance from the bottom of the hole after each periodic rapid advance and contact, and electric compensating circuit means responsive to the electric timing circuit means for actuating the control means to vary the rate of feed of the drive motor means to maintain the advance of the heating device at approximately a predetermined optimum distance from the bottom of the hole.

In the drawing:

Fig. 1 is a schematic side elevational view showing the automatically controlled and compensated thermal rock piercing apparatus embodying the invention;

Fig. 2 is a wiring diagram showing details of the automatic compensating control apparatus shown schematicall in Fig. l; and

Fig. 3 is a wiring diagram showing details of the motor control circuit for motor MS shown schematically in Fig. 1 of the drawing.

Referring specifically to the embodiment of the drawings, there is shown an elongated rock piercing blowpipe B which is suspended by a cable C in a hole H extending vertically downward in a body of rock R. Cable C passes over sheaves on the top of a vertical mast M, which is mounted on the front of a mobile rig A, and extends from the mast down to a reel or drum 10 carried on a floating support 12 pivotally mounted on a stanchion at 14 for movement in a vertical plane. Reel 10 can be driven by either of a pair of selectively operable motors, MS operable over a low speed range, and MF operable over a higher speed range. The motors MS and MF drive the reel 10 through a conventional planetary gear transmis sion PG which permits either motor to stand idle while the other motor is operating. Normally the motor MS is used for the advancement of the blowpipe into the hole and the motor MP is employed to raise the blowpipe. The automatic raising of the blowpipe when it strikes the bottom of the hole is clearly set forth in said US. Patent 2,679,381.

Blowpipe B and support 12 are approximately balanced against one another. As a result, the predominant ups oneness ward force, exerted on support 12 by the blowpipe and by a coil spring 16, holds the support in raised position as long as the cable supports the weight of the blowpipe.

During the piercing of a hole the blowpipe B is held steady by a'shoe-18 which slides on the mast M. Also, the teeth 19 of the blowpipe may be rotated by a suitable drive mechanism 20, such as described in United States Patent 2,338,093, wherein a turntable carries keys which fit slidingly in long keyways on the outside of the blowpipe. 7

When an obstruction, such as the bottom of the hole, is encountered during the normal advancement of the blowpipe during the piercing of a hole, the lower end of theblowpipe rests on the bottom and thus relieves the cable C of a substantial part of its weight. Meanwhile, reel It) continues to pay out cable so that the floating support 12 tilts downwardly about its pivot 14 in response to the reduced force exerted thereon 'by the blowpipe, which causes the predominant force on the support to be in a downward direction.

The downward tilting of the floating support 12 energizes a control circuit (not shown) described and claimed in said United States Patent 2,679,38l,'which operates to energize the drum motor to efiiect rotation of drum and take in cable. This causes the blowpipe to automatically retract a predetermineddistance when the bottom of the hole is encountered.

The automatic compensating control apparatus of the invention may be superimposed on this prior automatic retraction control apparatus. The instant device operates entirely in conjunction with the motor designated MS in the drawing Fig. 1. This motor is the motor of Fig. 3 and together with the generator constitutes a Ward- Leonard variable speed driving system. The motor MP is a constant speed A.C. motor and is used for rapid hoisting at a known speed. The automatic compensating control 22 includes a cycle timer 24, a sequence timer 26 and a rheostat motor circuit 27 for positioning the automatic motor and generator field rheostats shown in Fig. 3 connected in parallel with the'cycle timer and the sequence timer. Cycle timer 24 comprises a coil-operated electrical clutch 31 and synchronous motor 32' which operates so that the motor 32 acting through the clutch 3 actuates a plurality of contacts 38 after'the timed interval. The cycle timer functions to determine the periodicity of the measuring and compensating functions solenoid 40 closes normally opened contacts 40a in the generator field circuit and opensnormally closed contacts 4% in the (automatic) motor MS field circuit. The operation of these contacts puts full voltage across the generator field and full shunt resistance in the motor. field, resulting in a high rate of .motor speed at arapid blowpipe advancement into the hole.

Concurrently therewith, the energization of solenoid 40 also operates to close normally opened contacts 400 in series with the sequence timer, thereby energizing the sequence timer circuit, which comprises the combination of a magnetic clutch coil 48 a magneticv clutch (not shown) and motor 56 which drives a cam shaft (not shown). The sequence timer motor 50 activates the

relays

62, 64 and 70 through the cam activated

contacts

52, 54 and 56 in the compensator control system and contact 34 in the cycle timer circuit. Upon energization of the sequence timer'26, normally opened contacts 52 which function as holding contacts for the sequence timer, close ti. immediately and open after a predetermined period, for example 30 seconds; normally opened contacts 54 close immediately and open after a time period, for example 8 seconds; normally opened contacts 56 close after a time period, for example 8 seconds and open after 14 seconds; and normallyclosed contacts 34 in the cycle timer circuit open after a time period, for exarnple,"2() seconds. This latter period merely sets a predetermined maximumtime during which the blowpipe will be driven downthe hole on one cycle before striking the bottom. When 34 opens, contacts 46a and 4% open and close respectively.

During thisfoperation, the blowpipe has contacted the bottom of the hole causing the winch platform 58 to drop and causing normally opened contacts 60 to close. The

closing of contacts 60 closes the

circuitthrough contacts

52, 54 and solenoid 62 to energize solenoid 62 and soleno-id 64. The energization of solenoid 64 closes normally opened contacts 620, thereby assuring the continued energization of solenoid 62 even though the winch platform contacts 60 open due to the retraction of the bl0- pipe by the operation of the automatic control apparatus disclosed in'United States Patent 2,679,381. Additionally, the energization of solenoid 64 causes normally closed contacts 64a to open and prevents the energization of solenoid 7i).

The energization of solenoid 62 efiects a closing of contacts 62a and 62!; in the rheostat motor circuit, thereby energizing the rheostat motor armature 76 and series field 73 through line 80. This causes the rheostat motor to rotate in the direction which results in both, a reduction in shunt resistance 32 in the motor MS field'circuit, and an increase in resistance in the generator field circuit, both shown in Fig. 3 or" the drawing, to effect a reduction in the rate of normal blowpipe advance into the hole being pierced. Pairs of contacts are provided in the motor and generator field control circuits to permit a selection between manual and automatic control; handcontrolled contacts 36 provide for manual operation, and

hand-controlled contacts 88 provide for automatic operation. I

After the energization of solenoid 4! the closing and opening, respectively, of contacts 40a and as!) eifect the forward advancement of the blowpipe for a predetermined period'of time, i.e., 8 seconds determined by the opening of contacts 54 should the bottom of the hole not be contacted in that time due to the existence of too great a distance between the bottom of the blowpipe and the bottom of the hole. Under these conditions, winch platform 58 will not drop and contacts 60 will not close in the requiredtirne, thereby preventing the energization of solenoid 62 and contacts 56 will close to energize solenoid 70. The energization of solenoid 70, in turn, causes contacts 70a and 70b in the rheostat motor circuit to close energizingthe rheostat motor armature 76 andseries field 78 through line 80. This causes the motor to turn in a direction which will increase the shunt resistance 82 in the motor field and decrease the resistance 84 in the generator field to cause the motor' to pay out cable and advance the blowpipe at a greater rateinto the hole,

A typical example of the magnetic clutch used in both the cycle'tirner and sequence timer is described in sec. 5-129 of the standard Handbook for Electrical Engineers, 9th edition. The cycle and sequencetimers are of well known construction comprising synchronous motors driving rotatable shafts having suitable cams mounted thereon through the. magnetic clutches for mechanically activating electrical contacts associated with saidcams. Such timers also. include zero return springs which rotate the cam shaft back to the zero position when the clutch coil is deenergized.

Switch in series with the rheostat motor is I normally closed when the device is switched to automatic control, however it maybe opened manually by. the operator if he should merely wish to reciprocate the blowpipe up and down in the hole automatically without changing the speed of feed.

Thus, the automatic compensator control of the invention, when superimposed on the automatic control described and claimed in United States Patent 2,679,381, operates to increase or decrease the rate at which the blowpipe is normally advanced into the hole by periodically causing the blowpipe to bottom in the hole, by retracting the blowpipe after it has been caused to bottom, by measuring the time required for the blowpipe to reach the bottom of the hole and by adjusting the normal rate of blowpipe advance to maintain a predetermined optimum distance between the bottom of the blowpipe and the bottom of the hole.

The operation of an embodiment of the apparatus of the invention will now be described with reference to three operating conditions, wherein it will be assumed that 4 inches is the optimum distance to be maintained between the blowpipe and the bottom of the hole.

Condition (1): If the blowpipe is found to be less than 4 inches above the bottom before the hole at the time of sampling, the blowpipe speed is decreased automatically by the compensator; the amount of compensation being proportional to the distance between the blowpipe and the 4 inch reference level.

The time required to sample under optimum operating conditions is 8 seconds, i.e., with the blowpipe tip 4 inches above the bottom of the hole. The control, with the blowpipe located less than 4 inches above the bottom of the hole, must be such as to compensate for a devia-v tion from the 4 inch reference level. As for example, with the blowpipe 2 inches above the bottom of the hole, the time required to bottom would be 4 seconds (blowpipe advance at 30 i.p.m.). Associated with the sequence timer 26 are electrical contacts 54 which remain closed for the first 8 seconds of the sampling cycle. Since these contacts are closed for 8 seconds and the time required to bottom is 4 seconds, the difference in time (4 seconds) represents the amount of compensation necessary. Therefore, the rheostat motor decrease direction relay 62 would be energized for 4 seconds. This action permits the rheostat motor to turn the rheostat in the decrease direction and thereby cause the blowpipe to feed at'a slower rate during the next piercing cycle.

Condition (2): If the blowpipe is more than 4 inches above the bottom of the hole at the time of sampling, the blowpipe speed is increased automatically by the compensator; the amount of compensation being proportional to the distance between the blowpipe and the 4 inch reference level.

In this case, the control must compensate for any deviation from the 4 inch reference level. For example, with the blowpipe 6 inches above the bottom of the hole, the time required to bottom would be 12 seconds (blowpipe advance at 30 i.p.m.). Associated with the sequence timer 26 are electrical contacts that close after 8 seconds and open after 14 seconds of the sampling cycle. Since it takes 12 seconds to bottom and the contacts close after 8 seconds, the difference in time (4 seconds) represents the amount of compensation necessary. Therefore, the rheostat motor increase direction relay would be energized for 4 seconds. This action permits the rheostat motor to turn the rheostat in the increase direction and thereby cause the blowpipe to feed at a faster rate during the next piercing cycle.

Condition (3): If tie blowpipe is 4 inches above the bottom of the hole at the time of sampling, no speed correction is made.

The time required to sample under optimum operating conditions is 8 seconds, i.e. with the blowpipe 4 inches above the bottom of the hole. Therefore, condition (3) represents blowpipe location for best results. The electrical contacts associated with sequence timer 26 behave in such a manner as to render both increase and decrease 6 compensations inoperative; hence no compensation is effected.

What is claimed is: v

1. In combination with a heating device suspended in a hole in a body being pierced and provided with a feed mechanism for raising and lowering said heating device, the improvement which comprises control means associated with said feed mechanism for varying the speed of said feed mechanism, electric circuit means for periodically actuating said feed mechanism through said control means to cause said heating device to rapidly advance to contact the bottom of said hole, means to measure the time required during said rapid advancement until said heating device contacts the bottom of said hole, means to retract the heating device a predetermined distance from the bottom of the hole, and means to actuate said control means to vary the rate of feed of said feed mechanism in accordance with said time measuring means to maintain a rate of feed which provides approximately, during the normal advancement of said heating device, a predetermined optimum distance from the bo'ttom of said hole being pierced.

2. In combination with a material piercing device for removing material from a body without physical contact between said device and the material removal zone of said body to form a hole therein and provided with a feed mechanism for raising and lowering said piercing device, the improvement which comprises control means associated with said feed mechanism for varying the speed of said feed mechanism; electric circuit means for periodically actuating said feed mechanism through said control means to cause said piercing device to rapidly advance to contact the bottom of said hole; electric timing circuit means responsive to the time required for said piercing device to rapidly advance to contact the bottom of said hole; means for retracting said piercing device a predetermined distance from the bottom of said hole after each perio'dic rapid advance and contact; and electric compensating circuit means responsive to said electric timing circuit means for actuating said control means to vary the rate of feed of'said feed mechanism to maintain the advance of said piercing device at approximately a pre' determined optimum distance from the bottom of said hole.

3. In combination with a heating device suspended in a hole in a body being pierced and provided with a feed mechanism for raising and lowering said heating device, the improvement which comprises control means associated with said feed mechanism for varying the speed of said feed mechanism; electric circuit means for periodically actuating said feed mechanism through said control means to cause said heating device to rapidly advance to contact the bottom of said hole; electric timing circuit means responsive to the time required for said heating device to rapidly advance to contact the bottom of said hole; means for retracting said heating device a predetermined distance from the bottom of said hole after each periodic rapid advance and co'ntact; and electric compensating circuit means responsive to said electric timing circuit means for actuating said control means to vary the rate of feed of said feed mechanism to maintain the advance of said heating device at approximately a predetermined optimum distance from the bottom of said hole.

4. In apparatus for controlling the positioning of a heating device suspended by a cable in a body of rock and employing a feed mechanism for advancing said heating device including controlled drive motor means operable to pay out the cable and lower said heating device at a variable rate, the improvement which comprises control means actuating said drive motor means for varying the rate of feed of said drive motor means; electric circuit means for periodically actuating said drive motor means through said control means to cause said heating device to rapidly advance to contact the bottom of said hole; electric timing circuit means responsive to the time required for said heating device to rapidly advance to contact the bottom of said hole; means for retracting said-heating device a predetermined distance from the bottom of said hole-after each} periodic rapid advance andcontact; and electric compensating circuit means responsive to said electric timing circuit means for actuating said control means to vary the rateof feed-of said drive motor means to maintain the advance ofsaid heating device atapprox imately apredetermined optimum distance from the bottom ofi said hole. a

5. In apparatus for thermally piercing a body of rock and employing a heating device for directing heat against said bodyof rock to form a-hole therein, a frame having thereon an upwardly extending portion supporting cable guiding means above the hole to be made, a cable supportedby the guiding means and operably connected to said heating device, feed mechanism on the frame for taking up and paying out said cable for moving the heating device up and down in said hole, said feed mechanism including a rotary element around which the cable passes and whichis rotatably mounted in a support movably mounted on said frame, such rotary element being movable between first and second positions in response, respectively, to normal and lower tension of the cable, said feed mechanism also including controlled motor drive means operable to pay out the cable and lower the heating device at a variable feed rate and to take up cable for retracting the heating device when said'rotary support element reaches said second position in consequence of said heating device contacting the bottom of said hole, the improvement which comprises control means associated with said drive motor means for varying the and which is rotatably mounted in a support mo'vably mounted on said frame, such rotary element being movable between first and second positions in response, respectively, to normal and lower tension of the cable, said feed mechanism also including controlled motor drive means operable to pay out the cable, lower the heat ing device at a variable feed rate, and to takeup cable for retracting the heating device when said rotary support element reaches said second position in consequence of said heating device contacting the bottom of said hole, the improvement which comprises control means associated with said drive motor means for varying the speed of said drive motor means; electric circuit means including a'timing motor and associated cam driven contacts for speed of said drive motor means; electric circuit means of feed of said drive motor means in accordance with the time measuring means to maintain the advance of said heating device approximately a predetermined optimum distance from the bottom of said hole. 7

periodically actuating said drive motor means through said control means to cause said heating device to contact the bottom of said hole at a predetermined advancement speed, means including a second timer motor and associated cam driven contacts for measuring the time required for said heating device to contact the bottom of said hole and actuating the control means to vary the rate of feed of said drive motor means in accordance with the time requiredfor the heating device to contact the bottom of said hole, and means including the rotatably mounted means on the frame which is responsive to normal and lower cable tension for raising the heating device a predetermined distance in the hole whereupon the heating device is again advanced down thehole.

References Cited in the file of this patent UNITED STATES PATENTS