DIRECTIONS IN THE DEVELOPMENT OF HIGH-PERFORMANCE MACHINES FOR ROTARY DRILLING OF BLAST HOLES

O. D. Alimov

For drilling blast holes in rocks of medium hardness (\(f = 4—10\) on the scale of Prof. M. M. Protodyakonov), column-mounted electric drills have become most widespread in the mining and construction industries of the USSR. These drills are installed on special columns braced between the floor and the roof of mine workings.

In the USSR, two types of column-mounted electric drills are produced serially: EBK-2m and EBK-2A, whose characteristics are given in Table 1. The kinematic scheme and design arrangement of the drills are identical [1]. In column-mounted drills of the EBK-2m type, the electric drive of the reducer of the feed and rotation mechanism, the safety clutch, and the switch are mounted in one aluminum-alloy housing. For installation on a column or manipulator, the drill is provided with two trunnions. As the pri-

Table 1

* The rotation speed and feed rate are changed by replacing gear wheels.

water is a squirrel-cage asynchronous electric motor with an hourly rating of 2.7 kW.

For rotation and feed of the drilling tool in the EBK-2m drill, a screw differential mechanism is used (Fig. 1), which is also widely employed in other drilling machines. Feed of the drilling tool to the face relative to the stationary body of the drill is effected by the difference in rotational speeds of the screw—spindle 1—and the travel nut 2. Rotation is transmitted to the lead screw from electric motor 3 through a three-stage gear reducer (gears 4–9) and bushing 10. Bushing 10 is connected to gear 9 and has, on its inner surface, two key projections, which

Fig. 1. Kinematic diagram of the EBK-2m drill.

1 — spindle; 2 — feed nut; 3 — motor; 4–9, 13, 14 — gears; 10 — bushing; 11 — cam-friction clutch; 12 — shaft; 15 — spring of the friction clutch; 16 — control handle; 17 — drill body.

enter the keyways of the lead screw 1, milled along its entire length. The rotational speed of the screw spindle is changed by replacing gears 4–7. Nut 2 is rotated by the same motor as the lead screw, through the gear reducer with gears 4–7, the safety cam-friction clutch 11, shaft 12, and gears 13, 14. The screw and the nut have a left-hand thread with a pitch of 20 mm. The gear ratios of the reducers are selected so that during drilling nut 2 overtakes screw 1 and feeds it, together with the drilling tool, to the face. The feed rate of the drilling tool is determined by the formula

\[ V_1 = h(n_1 - n_2)\ \text{mm/min}, \]

where: \(h\) is the screw pitch, mm;
\(n_1\) is the number of revolutions of the nut per minute;
\(n_2\) is the number of revolutions of the screw per minute.

The drilling speed can be changed by replacing gears 13, 14, and also by slippage of the friction disks—

one clutch. The friction clutch, by means of preliminary tightening of spring 15, is adjusted to transmit to the feed nut 2 a definite torque. The factory setting of the friction clutch provides a feed force of 600 kg. If, during drilling, greater resistance arises, the clutch disks slip and the feed rate decreases. In this way the drill mechanism is protected against overload.

Rapid withdrawal of the tool from the face for changing the tool, or after completion of drilling a blasthole, is carried out by braking the part of the mechanism that transmits rotation to nut 2. For this purpose the cam-and-friction clutch, by means of handle 16, is moved back to the stop (position of handle II). The clutch cams come out of contact with the cams of gear wheel 7, and the clutch is braked against the housing of the drill reducer 17.

Since the movable part of the cam-and-friction clutch is connected by a key to shaft 12, shaft 12, gear wheels 13–14, and nut 2 are braked together with the clutch. In this case the drilling tool is withdrawn backward at the speed \(V_2 = hn_2\). In practice this speed is up to 6000 mm/min. For rapid advance of the tool to the face, for example after changing the tool, the same procedure is used, but the motor is first reversed. Reversing of the motor is carried out by a drum-type electric switch mounted in the drill housing.

Thus, the kinematic diagram of a drilling machine with a screw differential device ensures the performance of all operations necessary in drilling (rapid advance of the cutter to the face, drilling, and rapid withdrawal of the drilling tool from the face). At the same time, the design of the drilling machine itself is simple and compact. This explains the widespread use of mechanisms of this type in drilling machines for various purposes.

A disadvantage of the EBK-2m type drill design is that it does not permit the drill to be set, during the drilling process, to optimum drilling conditions, since for this purpose the replaceable gears must be changed. The latter can be done only after disassembling the drill. Owing to the difficulty of replacing the gear wheels and the absence of a method for selecting optimum drilling regimes for different mining and technical conditions, replaceable gear wheels are in most cases not used in mines, and drilling is carried out at the regimes for which the drill is set at the factory, i.e., at feed rates of 180–200 mm/min.

A second disadvantage of drills of this type is the insufficient strength and short service life of the machines. The guaranteed service life of EBK-2m column-mounted drills is 2 years, but, as practice has shown, the drills fail considerably earlier. The weakest part of the drill is the nut of the lead screw.

of the screw, which fails because of intensive abrasive wear of the thread turns. Wear of the nut is intensified by the presence of two longitudinal grooves on the lead screw. The service life of the nut does not exceed 4 months.

In recent years, the manufacturers of column drills have not achieved substantial results in improving the quality of parts and increasing the service life of drills.

For a long time, one of the principal shortcomings of drills of the EBK-2m type was considered to be their bulkiness and heavy weight—120 kg. Indeed, installing drills weighing 120 kg or more on an expanding column of the KEB type, which has no special devices for moving the drill at the face, is a very labor-intensive operation. On this basis, many innovators and researchers worked on creating a lightweight column electric drill. One of the most successful variants of such drills is the EKM-2 electric drill, created at the suggestion of Prof. Mikhailov [7]. In this drill, as in the EBK-2m drill, a screw differential mechanism is used for rotating and feeding the drilling tool, but the weight of the drill has been reduced almost by a factor of 2 (65.7 kg instead of 120 kg for the EBK-2m).

The reduction in the weight of the drill was achieved by means of a number of design solutions, including the use of a more compact flanged electric motor with ventilation. Unfortunately, the Konotop Mechanical Plant, which produced a pilot batch of EKM-2 drills, did not eliminate a number of design shortcomings of the drill inherent in every new design, and discontinued work on drills of this type.

It is entirely possible to create column electric drills lighter than the EBK-2m, and capable of operation, with motors of 2–2.5 kW, provided that higher-quality materials and a higher manufacturing technology are used. An example of this is the Dina-1 drill, serially produced in the GDR. This electric drill has a design analogous to the EBK-2m and the same motor power, but its weight is 38 kg less—82 kg.

An even more substantial reduction in the weight of column drills, with the same power, is possible by creating, for mines not hazardous with respect to gas and dust, electric drills not in explosion-proof construction, and for mines hazardous with respect to gas and dust—drills with pneumatic rotary motors. By using screw differential mechanisms and rotary pneumatic motors, column drilling machines weighing 45–50 kg can be created. However, drills with pneumatic drives will have limited application in the near future. Such drills will be used chiefly in mines that are supercategory with respect to gas and dust and in mines where there is a sufficiently powerful pneumatic system. For the majority of coal mines of the Soviet Union, however, where pneumatic power is absent, high-performance electric drills must be created.

In solving this problem, the task of creating light column-mounted electric drills, in our opinion, should not be the main and decisive one. It is impossible to substantially increase drillers’ labor productivity and the rate of driving workings without increasing drilling speeds. As studies of rotary drilling regimes for rocks with hardness \(f = 6 \div 12\) [3—5, 11] show, with the present design of the drilling tool and intensive removal of drill cuttings it is possible to ensure rotary drilling speeds of up to 3000 mm per minute. This is 15 times higher than the drilling speeds of EBK-2m drills with factory adjustment. But to operate under such regimes the drill must have a motor with a power of 4—5 kW. The weight of a modern electric motor of such power in explosion-proof design exceeds the weight of the EBK-2m drill.

To ensure operation under optimum regimes, the drilling machine must have sufficiently advanced devices for regulating the rotational speeds of the bit and the feed. This will also lead to a complication of the machine and an increase in its weight. Taking this into account, the problem of reducing the labor required to reposition drilling equipment at the face can be solved only by creating more advanced mounting devices—manipulators for installing drilling machines on loading machines and drilling carriages.

Many domestic and foreign research and design teams are working on the creation of electric drills that make it possible, during drilling, to vary the rotational speeds of the bit and the feed rates. In recent years new column-mounted drills have been created by the Kuznetsk branch of “Giprouglemash”—the PEB (rock electric drill)—and by the Konotop Mechanical Plant—the ESGP (electric drill with hydraulic feed). The principal distinguishing feature of these drills is the use of hydraulic feed, which, according to the designers’ intention, should provide stepless regulation of the feed force and feed rate directly during drilling.

The PEB-2m rock electric drill [8] consists of a motor with a mechanism for rotating the drilling tool and a piston hydraulic feed mechanism. Rotation of drilling tool 1 (Fig. 2) is carried out by motor 2, with a power of 4.5 kW, through a two-speed, three-stage gear reducer 3. Switching speeds and switching off bit rotation are carried out by means of gear-wheel block 4.

Gear wheels 5 and 6 are fastened by means of a key on spindle 7. One end of the spindle is connected by cams to feed cylinder 8. On the inner surface of the other end of the spindle there are projections that enter the grooves on the surface of hollow rod 9. Depending on whether gear-wheel block 4 is engaged with gear wheel 5 or 6, the spindle rotates at 192 or 341 revolutions per minute. One-

simultaneously with the spindle 6 the feed cylinder 9 rotates. At the end of the hollow feed rod a chuck 11 is mounted for fastening the drilling tool 1. The presence of the hollow rod makes it possible to insert into the machine a drill 2–2.5 m long, so that a part of the drill 1.5 m long is inside the hollow rod. After the hole has been drilled to the amount of the machine feed travel—400 mm—the driller, having released chuck 11, without removing drill 1 from the hole, moves the spindle to the extreme rear position. The drill is again fastened in the chuck, and drilling of the hole continues. With a hollow feed rod length of 1500 mm and a feed travel of 400 mm, it is possible, without changing the rod, to drill

Fig. 2. Kinematic diagram of the PEB-2 m:
1—drilling tool; 2—motor; 3—reducer; 4—gear block for shifting speeds; 5, 6—gears; 7—spindle; 8—cylinder; 9—rod; 10—piston; 11—chuck; 12—hydraulic distributor; 13—seals.

a hole to a depth of 1.6–1.8 m. For this it is necessary only four times to refasten the rod in the spindle chuck. Such a design of the connection of the drilling tool with the machine makes it possible to somewhat reduce the time spent on auxiliary operations.

The movement of piston 10 is effected by water, which is delivered to the feed cylinder by pump 12. Part of the water entering the cylinder through the opening in the drill and in the drill bit is used for flushing the hole.

Regulation of the feed speed is carried out by means of back pressure in the return-stroke cavity of the hydraulic cylinder. The back pressure is regulated by a throttle built into distributor 12. For feeding with a force of about 600 kg, it is necessary to provide a pressure in the feed cylinder of 12 atm, and for feeding with a force of 1000–1500 kg, respectively, 20–30 atm. Such pressures can be provided only by a special pump, with good seals 13 at the points of contact of the rotating feed cylinder 8 and rod 9 with the body and other parts of the drill.

A calibrated plug is installed in the internal bore of the rod; it prevents excessive consumption of water for flushing. In this way the required pressure is maintained in the feed cylinder.

The PEB-2m drill is supplied with water by means of a separate pump with a capacity of 40 l/min at an operating pressure of 15 atm. To drive such a pump, a motor of 11 kW is required. The weight of the PEB-2m electric drill was 130 kg, and the weight of the additional pump unit about 300 kg.

In our opinion, the basic layout of the PEB-2m drill has the following shortcomings: the drill, together with the pump unit, is cumbersome; for normal operation of the drill there are required

Fig. 3. Kinematic diagram of the ESGP-3a:
1—motor; 2—reducer; 3—spindle; 4—rod; 5—chuck; 6—cylinder; 7—piston;
8—oil reservoir; 9—gear pump; 10—toothed wheels; 11—throttle;
12—hydraulic distributor; 13—filter; 14—plug; 15—speed-shifting handle.

seals of very high quality, complicated in design; the use of mine water for hydraulic feed inevitably leads to corrosion of the feed cylinder and frequent clogging of the calibrated holes in the drill rod.

Unlike the PEB-2m, the hydraulic system of the ESGP-3a drill (Fig. 3) uses machine oil and a closed-type hydraulic circuit; the drive of the pump and of the drill-rotation mechanism is from one and the same motor. The ESGP-3a electric drill consists of electric motor 1 with a switch, a two-speed reducer for rotating the drill, and a hydraulic system for feed. Transmission of rotation from spindle 3 to the piston rod 12 and to the drill chuck 5 fastened to it is accomplished by means of flats milled along the entire length of the rod. Such a connection ensures transmission of torque to rod 2 and free longitudinal displacement of rod 2 relative to spindle 1. Unlike the PEB-2m, the cylinder 6 and piston 7 of the hydraulic feed in the ESGP-3a do not rotate. The rod is connected to the piston by means of radial

and thrust ball bearings. This design solution somewhat simplifies the construction of the seals.

The fluid is fed from reservoir 8, which forms part of the drill body, into the feed cylinder by a gear pump. The gear pump is driven by the motor through a single-stage toothed reduction gear, which reduces the speed from 2700 rpm on the motor shaft to 1000 rpm on the pump shaft. The pressure in the hydraulic system during drilling can be regulated manually by means of bypass valve–throttle 11.

According to the designers’ calculations, with the adopted parameters of the pump and feed cylinder, and with spindle oil used as the fluid, a pressure of up to 60 atm can be obtained in the hydraulic system of the ESGP-3a drill, which will provide a feed force of 1700 kg. Changing the direction of tool feed—forward for drilling or backward to withdraw the tool from the face—is accomplished by supplying oil to one or the other cavity of the cylinder.

When drilling with the ESGP-3a drill, the drilling cuttings are removed from the blasthole by the auger device of the drill or by flushing. The water supply for flushing is lateral. For this purpose, a special coupling is installed between the chuck and the piston-rod.

In 1955–1956, comparative tests of column-mounted electric drills were conducted in Kuzbass and Donbass. The electric drills tested were EBK-2m with factory adjustment, EBK-2m adjusted to the most expedient operating regimes, and the new PEB-2m and ESGP-3a drills. In advance, for the PEB-2m and ESGP-3a drills, the most expedient drill rotation speeds were selected by means of replaceable gear wheels. During drilling, the drills were mounted with the aid of MBM-1 manipulators on loading machines. Comparative production tests showed [8] that the PEB-2m and ESGP-3a drills, as well as EBK-2m drills with special adjustment, provide drilling of blastholes in the hardest rocks of the Prokop’evsk–Kiselevsk district at a machine speed of 0.6–0.8 m/min. At the same time, the service life of drill bits before resharpening when drilling with flushing is 7–17 running meters, and when drilling without flushing, 5–8 running meters of blasthole. This is several times greater than the service life of bits when working with EBK-2m electric drills with factory adjustment.

All this is an indisputable success on the path toward improving existing machines and creating new, more productive ones.

The tests revealed a number of shortcomings in the PEB-2m and ESGP-3a drills, of which, in our opinion, the principal ones are:

1. The complexity of the design and the inadequate quality of the hydraulic-system seals.

1. The power of the electric motor of the ESGP-3a drill—2.5 kW—proved insufficient for the simultaneous drive of the drill-rod rotation mechanism and the hydraulic system.

2. The effort to reduce the weight of electric drills led to an excessive reduction in the strength of individual parts. Thus, for example, the service life of the thrust bearing of the hydraulic cylinder of the ESGP-3a is only 150–250 hours.

Eliminating the shortcomings listed above will inevitably lead to an increase in the weight of individual assemblies and of the machines as a whole. On the basis of test results, the Kuznetsk branch of Giproglemash and the Konotop plant are improving the designs of the drills. For the time being, however, the PEB-2m and ESGP-3a machines are more complex to manufacture and less reliable in operation than the EBK-2m.

The results of comparative tests of PEB-2m- and ESGP-3a-type drills and EBK-2m drills adjusted to higher operating conditions made it possible [9] to reveal yet another substantial shortcoming, to which, earlier, during operation of EBK-2m drills with factory adjustment, no special attention had been paid. This shortcoming consists in the fact that, when servicing column-mounted drills, the worker-driller is forced to spend a considerable amount of time on auxiliary operations. Moreover, when drilling at higher operating conditions, the time spent on auxiliary operations exceeds the time spent on drilling itself. As a result, the new machines, while having a drilling speed 4–5 times greater than EBK-2m drills (adjusted to ordinary operating conditions), reduce the time required to drill one face by only 1.5–2 times. If, however, one compares the results obtained in testing the new drills with the test data for EBK-2m drills adjusted to the most productive operating conditions, it turns out that the productivity advantages of the new drills are even less substantial. The increase in drilling speed with the new drills in machine time amounts to no more than 18%, and the increase in productivity in total time (without downtime) is no more than 15%.

Figure 4 shows how large a proportion, in terms of time, such auxiliary work as replacing the drilling tool, dressing, setting up the drill, and collaring occupies in the drilling cycle. When drilling with ESGP-3a, PEB-2, and EBK-2m drills adjusted to optimum operating conditions, the total time of auxiliary work is approximately 3 times greater than the machine drilling time. The excess of auxiliary-work time over the time of drilling proper does not allow one worker to service several machines, as was possible when drilling with EBK-2m drills adjusted to ordinary operating conditions. All this adversely affects the labor productivity of the workers and significantly reduces the effect of using the new, more complex and expensive ESGP-3a- and PEB-2m-type drills.

On the basis of the data presented above, it is evident that achieving a sharp increase in labor productivity in drilling

is possible only with simultaneous improvement of drilling conditions and a sharp reduction in the duration of such auxiliary operations as changing the tool, setting up the drill for drilling, and collaring.

To accomplish this, in our opinion [9], when creating new high-performance drills it is necessary to abandon the existing basic layout of column-mounted drills, which is the same for the EBK-2m drill and for the newly created ESGP-3a and PEB-2m drills. The essence of this layout is that the drilling machine proper (motor, reduction gear) is fastened to a column or manipulator and remains stationary during drilling. The spindle of the machine with the drilling tool, in addition to rotation, performs a translational motion by means of special devices (a differential-screw device in the EBK-2m, or a hydraulic device in the PEB-2m and ESGP-3a). The maximum feed stroke in such drills does not exceed 900 mm.

As noted above, the principal advantage of this layout is the possibility of creating drills that are most compact and light in weight.

In addition, the basis for creating column-mounted drills according to such a layout in the past was the circumstance that carbon-steel bits were used for drilling. The rapid blunting of such bits required changing the drilling tool 3–4 times when drilling a single hole. In view of this, it was impractical to choose a maximum spindle stroke of drilling machines greater than 700–900 mm.

At present, this drilling method cannot ensure the fullest use of the advantages of modern drilling tools and increased drilling conditions, because of the considerable time expenditures for auxiliary operations. Drilling is carried out with bits tipped with hard alloys, which, under rational flushing drilling conditions, make it possible to drill holes 5 to 8 m long in rock of hardness \(f = 6 \div 8\) without replacement. In this connection, it has become possible to eliminate the intermediate three- or fourfold changes of tool when drilling each hole and thereby sharply reduce the time spent on auxiliary operations. For this it is necessary to create machines with continuous feed of the tool over the entire length of the hole—1.8–2.0 m. It is possible to obtain such a tool stroke in drills built according to the above-mentioned basic layout of the EBK-2m, ESGP-3a, and PEB-2m drills. But with a drill length of 2 m, without additional devices for supporting and guiding the drill steel, the process of starting the hole (collaring) will be associated with a considerable expenditure of time, massive breakage of the tool, and inevitable injuries. It is difficult to create reliable and sufficiently compact devices for collaring for such drills.

Moreover, increasing the spindle travel to 2 m has an unfavorable effect on the overall dimensions and weight of such a machine. With a feed of 2 m, the length of the machine will be approximately 2.6–2.7 m, and its installed dimensions in the face, together with the tool, 4.8–5 m. Faced with these shortcomings, the designers of the ESGP drill increased the feed travel only slightly, taking it as 900 mm as against 890 in the EBK-2m, which did not eliminate the threefold changing of rods during the drilling of a single blast hole. Replacement of the complete set of tools by re-clamping it in the chuck (PEB-2 drills) likewise did not lead to a significant reduction in the time spent on auxiliary operations.

The problem of reducing the time for the auxiliary operations noted above is solved most simply if column-type drills are designed according to the scheme of modern column-type drilling hammers, for example of the KTsM-4 type. The distinctive feature of this basic scheme is that the drilling machine with the tool moves during drilling along fixed guides. The length of the guides can be selected depending on the required depth of the blast hole and the corresponding length of the tool. Thus, for drilling blast holes 2 m deep, the length of the guides, allowing for the dimensions of the feeding mechanism, should be about 2.5 m. This value also determines the overall length of the drilling rig in the face. Consequently, such a machine will be more compact than machines built on the basis of the schemes used in the EBK-2m, PEB-2m, and ESGP-3a.

The presence of long guides, closely fitting the face, makes it possible to equip such “long-travel drills” with reliable in-service and compact devices for guiding the drilling tool. This, in turn, will make it possible to reduce to a minimum the time spent on barring-down, setting up the drill, and collaring. Such machines must operate under conditions that ensure the highest drilling speed.

To reduce the labor intensity of operations for moving the machine from one blast hole to another, long-travel machines, as well as the ESGP-3a and PEB-2m, should be mounted on loading machines or on special drilling carriages with the aid of manipulators.

For drilling rocks of low strength, \(f = 4 \div 6\), light long-travel machines should be developed using hand drills of the ER-5, ERP-5 types and light devices for holding and feeding the drill.

Table 2 gives the technical characteristics of the recommended long-travel electric drills, compiled with allowance for the results of investigations of rotary drilling conditions [2–4, 11] and drilling-and-blasting work specifications [10].

Figure 4 compares the results of drilling the face with EBK-2m, PEB-2m, and ESGP-3a drills with the results of the proposed long-travel machines operating under the same ...

Table 2

regimes. From Fig. 4 it is evident that the long-stroke machine, by reducing the time spent on auxiliary operations, can reduce the total time for drilling off the face, compared with the same indicators when operating the PEB-2m, by 1.45—1.65 times, and when operating with ordinary EBK-2m drills by more than 3.5 times.

An equally important advantage of the long-stroke machine is that its auxiliary-work time is less than machine time. As a result, one worker can service two drilling machines. An additional increase in labor productivity can be achieved by increasing the depth of the holes to 3—3.5 m. For effective use of long-stroke machines in this case, it will only be necessary correspondingly to increase the length of the guides without changing the rest of the machine design. The effect from using long-stroke drills in heading work will be the greater, the more advanced the equipment and organization of labor employed in the other operations of the heading cycle.

In addition to long-stroke drills with electric drive, for the conditions of coal and ore mines there should be produced long-

crawler drilling machines with pneumatic and hydraulic drives. In particular, for the conditions of workings in the Kuzbass, long-stroke drills with electric drive are most expediently used in mines of the 1st and 2nd categories with respect to gas and dust; with pneumatic drive—in mines of the 3rd category and supercategory mines; and with hydraulic drive—in mines and sections where coal extraction and transport are carried out hydraulically.

Drills may have either a common drive for rotation and feed, or individual drives (a separate motor for rotating the drill bit and a separate one for feed).

Legend: auxiliary operations, min.; drilling, min.

Bar labels:

• EBK-2m: $n = 305$ rpm; $V = 275$ mm/min; $F = 1000$ kg. Drilling: 7.7 min; auxiliary operations: 7.8 min.
• EBK-2m: $n = 408$; $V = 750$; $F = 1000$. Drilling: 2.6 min; auxiliary operations: 8.9 min.
• PEB-2m: $n = 300$; $F = 650$. Drilling: 2.6 min; auxiliary operations: 7.4 min.
• ESGP-3a: $n = 425$; $F = 800$. Drilling: 2.3 min; auxiliary operations: 8.1 min.
• Long-stroke drill. Drilling: 2.6 min; auxiliary operations: 3.4 min.

Drilling with flushing.

Fig. 4. Time expenditures for drilling one linear meter of blasthole by various electric drills in rocks of medium hardness.

As feed mechanisms, screw, rack, chain, and hydraulic mechanisms may be used. The type of drive and the type of feed mechanism are decisive in selecting the kinematic scheme of a long-stroke machine, which must be simple in construction and convenient in operation.

Studies carried out by the Department of Mining Machines and Mine Transport of the Tomsk Polytechnic Institute have shown that, despite the simplicity of the basic schemes of long-stroke drilling machines, in designing them it is necessary to solve a number of complex problems. The most difficult of these is the creation of feed mechanisms for machines with electric drive.

In the course of solving these problems, the author proposed a number of basic layouts,* on the basis of which several working designs of drilling machines were developed. According to these designs, the Department of Mining Machines and Mine Transport, together with the mechanization laboratory of KuzNIIUI and the TEMZ plant, manufactured the drilling machines EBR-1, EBV-1, and DEGP-1, which are undergoing laboratory and production tests. All these machines are intended for drilling rocks with hardness \(f = 6—10\). Rotation of the drill is effected by an electric motor, and removal of drill cuttings from the hole is by flushing or by helical rods.

Fig. 5. Electric drill with rack feed EBR-1:
1 — motor; 2 — reducer; 3 — flushing coupling; 4 — drill; 5 — feed gear; 6 — rack; 7 — lunette; 8 — compensator screw; 9 — slide; 10 — stop; 11 — manipulator boom.

The difference between the machines lies in the type and design of the feed mechanisms.

In the electric drilling machine with rack feed—EBR-1—the drive for rotation and feed of the drill is common. The electric drill (Fig. 5) consists of electric motor 1 with reducer 2 and guides with rack 6. Rotation of spindle 1 (Fig. 6) is effected from asynchronous motor 2 through two-stage gear reducer \(3—4—5—6—7\). Feed of the drill along the guides occurs when gear wheel 15 rolls along rack 16, fastened to one of the machine guides. Rotation is transmitted to gear wheel 15 from motor 2 through the transmission system \(3—4—5—6—19—8—9—10—11—12—14—13\) when

* O. D. Alimov, Report “Investigation of drilling machines for the purpose of finding means of increasing the labor productivity of drillers and the rate of driving mine workings in rock.” Tomsk, 1956. Technical archive of KuzNIIUI.

drilling, or 3—4—5—6—19—8—17—18—14—13 in reverse. Friction clutch 19 is a safety clutch. Switching from forward travel (whose speed is 0.6–2.0 m/min) to reverse travel (speed 4–6 m/min), and vice versa, is accomplished by reversing the motor. Changing the feed rate and the rotational speed of the drill is achieved by replacing gear wheels 3, 4, 11, 12.

To compensate for the drilling machine’s movement away from the face, when moving the boom of an MBM-1 manipulator, the guides of the EBR-1 feeder can move relative to the boom of the manipulator. This movement can be effected either by a screw pair manually (Fig. 5) or by a piston hydraulic jack. As the working fluid in the compensator jack, water used for flushing the blasthole is supplied. Preliminary pressing of the guides toward the face facilitates collaring and eliminates skewing of the drill in the blasthole during drilling.

Fig. 6. Kinematic diagram of the EBR-1 long-stroke drill:
1—spindle; 2—electric motor; 3—9, 11, 12, 17, 18—gear wheels of the reducer; 10—jaw clutch; 13, 14—worm gear; 15—gear wheel; 16—rack; 19—safety clutch.

The advantage of the EBR machine is the presence of a single common drive, as well as the simplicity of controlling the machine. The machine can be used with modern mounting devices, for example the MBM-1u. The drilling speed of the EBR-1 is changed only by replacing gear wheels, which is a drawback of the drilling machine. This drawback has been eliminated in another drilling machine, the EBV-1.

The EBV-1 electric drilling machine with screw feed consists of a drill rotator and a screw feeder with hydraulic drive. The design of the EBV-1 rotator is maximally simplified and consists of electric motor 1 (Fig. 7), a single-stage planetary reducer 2, and device 3 for supplying water to drill 4. The feed of the rotator along the guides

is carried out by lead screw 5, which is driven by a hydraulic motor of gear type 6 through two-speed reducer 7.

The drill rotation speed during drilling remains constant; the feed speed and force can be varied.

The accelerated reverse travel of the rotator and the drilling tool fastened in it is accomplished by reversing the hydraulic motor. At the same time, the speeds in transmission reducer 7 are switched automatically. As the hydraulic motor of the feed mechanism, a gear pump from the S-153 loading machine is used. The hydraulic system is designed for an operating pressure of 50 atm. For the preliminary pressing of the drill guides against the face, a special hydraulic jack is provided. A drawback of the drill

Fig. 7. Kinematic diagram of the long-travel drill EBV-1:
1—motor; 2—reducer; 3—coupling for supplying water to the drill; 4—drill; 5—screw; 6—gear pump; 7—reducer; 8—coupling for speed changing; 9—cylinder for speed changing; 10—jack; 11—oil tank; 12—filter; 13—pump; 14—hydraulic distributor.

EBV-1 is the comparatively low efficiency of the screw feed mechanism and of the gear hydraulic motor. In the future it is planned to replace the gear motor with a more economical plunger motor. Other basic machine layouts are also being sought that would not have the indicated drawbacks. One such layout has been implemented by the author in an experimental prototype of a long-travel electric machine with hydraulic feed—the DEGP-1 (Fig. 8). In this machine, as in the EBV-1, drill rotation is carried out by electric motor 1 with planetary reducer 2. The rotator is moved along the guides by means of piston hydraulic jack 5 and chain doubler 8. During the working stroke of the rotator, oil is supplied by pump 9 into chamber I of cylinder 5 of the hydraulic jack, and during the return stroke—into chamber II. Owing to the considerable diameter of rod 7, the useful piston area in chamber II is 4 times smaller than in chamber I. As a result, with the same quantity of oil supplied by the pump, the speed of the return-

the drill return stroke is 4 times greater than during drilling. To carry out the return stroke at a higher speed, the EBV-1 drill required a special two-speed reducer, which complicated the machine. The use of a piston feed device in the DEGP-1 machine instead of the gear motor in the EBV-1 also makes it possible to reduce the power expenditure for feed. However, the DEGP-1 machine is heavier and bulkier than the EBV-1.

The use of a hydraulic drive, with its inevitable and rather complex additional devices (a pump with motor, regulators and distributors, and other elements of the hydraulic system), for the feed mechanism of an electric drill at first glance unjustifiably complicates the drilling machine. But if one takes into account that the most

Fig. 8. Kinematic diagram of the DEGP-1 long-stroke drill:

1 — motor; 2 — reducer; 3 — water coupling; 4 — auger; 5 — feed cylinder; 6 — piston; 7 — rod; 8 — multiplier chain; 9 — pump; 10 — filter; 11 — oil tank; 12 — hydraulic distributor.

appropriate type of drive for manipulators and a number of other mechanisms of loading machines and drilling carriages is a hydraulic drive, and that in this case the hydraulic system can be common with the drilling machine, then under these conditions the use of a hydraulic drive for the feed mechanisms of electric drills will be the most appropriate. With considerable power of the hydraulic pump of the common hydraulic system, rotation of the auger of a long-stroke drill can also be effected by a hydraulic drive. Such a solution will make it possible to reduce substantially the weight and overall dimensions of the rotating unit of the drilling machine. To reduce the weight of the guides, it is advisable to make them riveted, from light alloys. A final answer to the question of the most appropriate designs of feed devices for long-stroke drills can be given only after detailed laboratory and production investigations.

Experience in the testing and operation of drilling machines with large feed forces in the USSR and abroad shows that

to ensure the reliable operation of such machines, it is necessary to mount them only on special carriages or on loading machines with the aid of manipulators. This conclusion applies entirely to long-stroke drilling machines. Manipulators for such machines must ensure rapid transfer of the machine from one blasthole to another, and must be sufficiently strong and rigid. The latter is necessary to prevent deviations of the machine, during the drilling process, from the specified direction and the resulting breakage of drills. At present, experimental models of long-stroke machines are being mounted on MBM-1 type manipulators available in mines. Because of their imperfections (manual drive, insufficient boom length, and an unreliable device for fixing the manipulators in the required position), these manipulators cannot ensure full use of the advantages of long-stroke drills. Therefore, simultaneously with the creation and improvement of long-stroke drilling machines, the necessary manipulators should also be created.

REFERENCES

1. V. K. Buchnev. Drilling-and-blasting operations. Ugletekhizdat, 1955.

2. V. K. Mikhailov. Drilling of blastholes. Metallurgizdat, 1947.

3. G. N. Pokrovskii. Investigation of the process of rock destruction during rotary drilling of blastholes with constant feed force. Candidate dissertation. Library of the TPI, Tomsk, 1954.

4. M. K. Tsekhin. Investigation of drilling-and-blasting operations and increasing their efficiency in driving horizontal workings in rock at the mines of the Prokop’evsk mine. Candidate dissertation. Library of the TPI, Tomsk, 1955.

5. A. D. Imas, V. L. Azarkh. Determination of drilling regimes for rocks. Ugletekhizdat, 1952.

6. D. P. Dukhovlinov. Mechanization of work in potash mines of the GDR. Mechanization of Labor-Intensive and Heavy Work, No. 6, 1957.

7. A. E. Demchenko. Column-mounted electric drill EKM-2. Collection of Works of DonUGI, No. 12, 1954.

8. Yu. K. Alikin. Experimental operation of rock drills with hydraulic feed. Ugletekhizdat, 1957.

9. O. D. Alimov, A. I. Volkov. Some directions in the creation of high-performance drilling machines for hard rocks. Collection 5, Research on Mining in the Kuznetsk Coal Basin. Kemerovo, 1957.

10. O. D. Alimov, V. M. Zakhlebnyi, A. S. Simonov. Principal factors determining the dimensions of a drilling installation. Izvestiya TPI, vol. 88, Tomsk, 1956.

11. O. D. Alimov, I. G. Lyanichev, Ya. A. Serov. Studies of regimes of rotary and rotary-percussive drilling. Article in the present collection.

NOTED MISPRINTS

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