JPS62193714A - Control device for drilling machine able to be fixed to work by electromagnetic base - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a drilling machine control device, and in particular,
Electromagnetic base (electromagnetic device) as a means of fixing to the workpiece
an electric drill having an annular cutting tool at its lower part;
The present invention particularly relates to a portable drilling machine control device equipped with a motor for controlling the feed of an electric drill (hereinafter referred to as a feed motor).

(Prior art) As is well known, when performing drilling work using an electric drill equipped with an annular cutter, a larger torque can be obtained and the cutting performance is superior compared to when using a twist drill. On the other hand, there is a possibility that an abnormally large load is applied to the annular cutter, which may damage the annular cutter or burn out the electric drill.

Therefore, when working with the annular cutter attached to an electric drill, the operator must always be careful not to place a large load on the annular cutter.

However, it is extremely difficult to recognize the magnitude of the load, in other words, to discern whether an appropriate load is being applied to the blade of the annular cutter, or whether an excessive or insufficient load is being applied.5 This can only be done by a single worker.

Therefore, if this drilling machine is operated by a beginner who is not familiar with its handling, it may cause damage to the annular cutter mentioned above or burnout of the electric drill, or in extreme cases, the annular cutter of the electric drill may be There is also a high risk that this could lead to confusion.

Furthermore, it is desirable to turn off the power of the drilling machine immediately after the drilling operation is completed, in order to save power consumption and to prevent breakage of the annular cutter.

However, with conventional drilling machines, the operator has to turn off the power switch of the drilling machine after realizing that the drilling work has been completed, which is very tedious for the worker. Its workability is also not very good.

In order to solve the above-mentioned drawbacks, the present inventors have conducted various research and development, and have already filed a patent application No. 1864-1986.
No. 73, No. 57-23741 and No. 59-2526
We have filed patent applications such as No. 97.

The invention of Japanese Patent Application No. 57-23741@ is equipped with a feed motor for advancing an electric drill toward a workpiece, and a control circuit of the electric drill is configured to control the magnitude of the load of the electric drill by controlling the current flowing therein. A detection unit is provided that detects based on the value, and when the detection output reaches the set level of the first stage, the feed of the electric drill is automatically stopped to reduce the load, and then the load is reduced. When this is detected, the feed of the electric drill is restarted, and when the second stage overload level is detected, both the rotation of the electric drill and the feed of the electric drill are automatically stopped. Similarly, when the electric drill is completed, the rotation of the electric drill and the feeding of the electric drill are automatically stopped.

Further, the invention of Japanese Patent Application No. 59-252697M provides a first detection circuit that stops the rotation of the feed motor when the load current flowing through the drill motor exceeds a first threshold; in addition to a second detection circuit that also stops the rotation of the drill motor when the load current exceeds the first threshold;
Measures are taken to stop the feed motor intermittently, thereby facilitating the removal of built-up edges formed on the tool and the evacuation of chips, so that large loads are not applied to the electric drill in a shocking manner. It is designed to prevent this from happening.

(Problems to be Solved by the Invention) The above-described conventional techniques had the following problems.

(1) If the feed motor is driven intermittently, the drilling efficiency will decrease accordingly.

(2) Conventionally, the rotation speed of the feed motor, and therefore the feed speed of the electric drill, was set to be almost constant, especially when the workpiece has a highly hard layer called "black scale" on the surface. In the early stage of drilling, the drill biting is poor, and the drilling position may become inaccurate or misaligned, and in severe cases, the drilling machine itself may be swung around.

The present invention has been made to solve the above-mentioned problems.

(Means and effects for solving the problem) In order to solve the above problem, the present invention provides that, immediately after starting the electric drill, that is, in the initial stage of starting machining, the electric drill moves forward by a predetermined distance. During the initial stage, or during the scheduled time after startup, the feed motor is driven by an AC half wave to bring it into a slow feed state, and after the initial stage has passed, the feed motor is gradually shifted to being driven by an AC full wave. , On the other hand, the load current flowing through the drill motor is detected, and the drive current of the feed motor is feedback-controlled according to the magnitude of the detected load signal, and when the load signal increases and exceeds the second upper limit value, the feed Both the motor and the drill motor are stopped in an emergency, and when drilling is finally completed, the system detects that the drill motor is no-load and the load signal suddenly decreases, and then stops both the feed motor and the drill motor. It is distinctive in its composition.

(Example) The present invention will be described in detail below with reference to the drawings, but before that, an outline of a drilling machine device suitable for applying the present invention will be described. FIG. 3 is a schematic perspective view showing the overall structure of a mechanical part suitable for applying the present invention, and FIG. 4 is a right side view thereof.

In these figures, 1 is a frame, 2 is an electromagnetic base attached to the bottom of frame 1, 3 is an electric drill installed on the front of frame 1 so that it can be raised and lowered either manually or electrically, and FM is electric drill 3. The feed motor 5 is an annular cutting tool attached to the arm of the electric drill 3.

Further, 39 is a manual lifting/lowering operation handle for manually feeding the electric drill 3, and 36 is a slide plate fixed to the electric drill 3.

The switch operation plate 37 is fixed to the slide plate 36 with thumbscrews 38. The switch operation plate 37 moves as the electric drill 3 descends, and when it descends to a predetermined position, it operates a limit switch Sl (described later with reference to FIG. 1).

40 is an operation handle for operating the starting switch PS, which moves in two steps and connects the three contacts 0 and 1 of the switch.
．． 2 (see Figure 1) in a predetermined order.

An operation control circuit constituting the main part of the present invention is built into the frame 1. Further, when positioning the electric drill, the punch 41 drops instantaneously due to the elastic force of the spring 42 that has stored energy in advance, and pierces the surface of the workpiece, which, in combination with the adsorption force of the electromagnetic base 2 described later, allows the punch 41 to be positioned. ensure that

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a timing chart for explaining its operation.

A. Immediately after starting, when the half-wave feed control power switch PS or rOJ of the feed motor FM is in the position, all power supplies are cut off, and the drilling machine control device shown in FIG. 1 is in a dormant state.

When the power switch PS is moved to the "1" position, the electromagnetic magnet MG is energized, and the electromagnetic base 2 of the electric drill is energized.
is attracted to the workpiece and positioning is performed. At the same time, the light emitting diode LED4 lights up to indicate that positioning is complete.

When the power switch PS is moved to the 12'' position, the AC power supply voltage is applied to the primary winding under the step-down transformer, so the rectifiers REF2 and REF3 operate to generate a DC voltage.

The DC output of the rectifier REF2 is adjusted to a constant voltage by a constant voltage device STB, and becomes a control voltage VCC. The control voltage Vcc is applied to the resistor R63 and the transistor Tr.
11.

As will be described in detail later, at this time the transistor Tr1
Since the base potential of C1, that is, the output of the OR circuit OR3 and the charging voltage of the capacitor C13 are at low level,
The transistor Tr11 is in an off state, and its collector potential is approximately equal to the control voltage Vcc.

Therefore, the control voltage VCC is applied to the light emitting diode LED6 of the relay SSR, and the light emitting diode LED
6 emits light. The light emission is applied to the triac TRC2, and the relay SSR becomes conductive. This energizes the drill motor ED and starts rotating.

The secondary voltage of the step-down transformer T is also half-wave rectified by the diode D4, and then passed through the resistor R36 to the transistor T.
Supplied to the base of r8.

Therefore, the transistor Tr8 conducts at a period of every AC half wave, and a pulse signal synchronized with the AC half wave is generated at its collector as shown by waveform (2) in FIG.
It is supplied to one input terminal of the OR circuit ORI.

Note that, at this time, the operational amplifier OP6 does not generate an output, as will be explained later. Therefore, the output of the OR circuit OR1 becomes a pulse signal synchronized with an AC half wave as shown by waveform (2) in FIG.

On the other hand, the secondary voltage of the step-down transformer T is rectified by a rectifier REF3, and the rectified output is applied to a series circuit of a resistor R34 and a zener diode ZD.

Therefore, a pulsed voltage that clips the full-wave rectified waveform at a predetermined level is generated across the zener diode ZD, as shown in waveform (3) in FIG.
3 to the base of the transistor Tr6.

Since the transistor Tr6 is conductive at a portion other than the vicinity of the zero crossing point of the AC waveform (1) in FIG. The signal is at high level, and the other areas are at low level.

Contrary to the transistor Tr6, the transistor Tr7 conducts near the snow catching point of the AC waveform (1) in FIG. It becomes low level at the part.

During the time when the collector of the transistor Tr7 is at a high level, the capacitor C8 is charged with the time constant of C8·R42, and when the transistor Tr7 becomes conductive, it is discharged via this with an extremely short time constant.

Therefore, the charging voltage of the capacitor C8, that is, the input voltage of the non-inverting input terminal of the operational amplifier OP7 changes in a sawtooth shape as shown by the solid line of waveform (5) in FIG.

The load current flowing to the drill motor ED is a current transformer CT.
and is detected by the rectifying and smoothing device R3C, and a load signal Eed is generated.

Initially when the drill motor ED is started, the drill motor E
Since D is unloaded, the load signal Eed is sufficiently small. Therefore, the non-inverting input terminal of the operational amplifier OP7 is larger than the inverting input terminal, and its high level output is supplied to the AND circuit AND1.

Therefore, the AND circuit AND1 generates the output of the OR circuit OR1, in other words, the same output as the collector potential of the transistor Tr8 shown in waveform (2) in FIG. 2, which is supplied to the gate of the triac TRC1.

In this way, the electric drill is fed at a relatively slow speed since the feed motor FM is driven by a half-wave of the AC waveform. As a result, the electric drill's blade eventually reaches the surface of the workpiece, and drilling begins from the hard part, the so-called black crust.

= 16- When this drilling starts, the load current of the drill motor ED gradually increases, and the load signal Eed rises.

Therefore, the operational amplifier OP7 generates a low level output when the level of the sawtooth signal supplied to its non-inverting input terminal is low, and generates a high level output when the sawtooth signal exceeds the load signal Eed. I come to do it.

As is clear, the lower the load signal Eed is, the earlier the high level output is generated, and the higher the load signal "ed is, the later the timing at which the high level output is generated is.

For this purpose, the timing when the AND circuit ANDI is opened by the high level output of the operational amplifier OP7, in other words, the triac TRC1 is triggered and the feed motor F
The phase in which the AC voltage is applied to M becomes earlier as the load signal Eed is lower, and becomes later as the load signal Eed is higher.

Therefore, the feed rate of the electric drill is determined by the drill motor E
The lower the load applied to D, the faster the speed; conversely, the higher the load, the slower the speed.

The load signal Eed is also supplied to the non-inverting input terminal of the operational amplifier OP4, and is compared with a reference value divided by resistors R16 and R17.

At the beginning of the start-up of the drill motor ED, the load is light, so the load signal Eed is small, the output of the operational amplifier OP4 is at a low level, the transistor Tr4 is conductive, and its collector is at a low level.

Therefore, capacitor C7 is not charged. That is, the terminal voltage of the capacitor C7 is at a low level, and the output of the inverter circuit IN2 is at a high level. The output of the inverter circuit IN2 is supplied to the inverter circuit IN3 and the first input of the AND circuit AND2.

The low level signal inverted by the inverter circuit IN3 is
Since it is supplied to the AND circuit AND2 as its second input, the output of the AND circuit AND2 becomes low level. The outputs of the OR circuits OR2 and OR3 maintain low level and do not make the transistor Tr11 conductive.
Relay SSR continues to operate. In this manner, drill motor ED and feed motor FM continue to be driven.

B. Transition of feed motor FM from slow feed to full wave feed control The low level charging voltage of capacitor C7 is also supplied to one terminal of NAND circuit NAN at the same time, so its output is set to high level and transistor Tr5 is turned off. Make it conductive. At this time, the potential of the collector of the transistor Tr5 is at a high level, and the capacitor C13 is charged via the diode D2. Therefore, the output of the operational amplifier OP6 is at a low level, and does not affect the output of the OR circuit OR1.

When the load on the drill motor ED increases and the load signal Eed rises roughly, the output of the operational amplifier OP4 is inverted and becomes a high level, and the transistor Tr4 is cut off. The collector of transistor R4 becomes high level, capacitor C7 is charged via resistors R20 and R22, and its terminal voltage rises. As a result, the inverter circuit IN
The output of inverter circuit IN3 drops to low level.
Since the output of the capacitor CI2 becomes high level, the capacitor CI2 starts to be charged through the resistor R60.

However, at this time, since the output of the inverter circuit IN2 is at a low level, the output of the AND circuit AND2 does not change, and the states of the circuits after the OR circuit OR2 do not change.

On the other hand, the terminal voltage of the capacitor C7, which gradually increases as described above, is supplied to one input terminal of the NAND circuit NAN. At this stage, as will be described later, the output of the operational amplifier OP5 does not change and remains at a high level, so when the terminal voltage rises to a certain value (SHI) [see waveform (14) in Figure 2] ], the output of the NAND circuit NAN is inverted and becomes a low level. As a result, the transistor Tr
5 becomes conductive, the charge in the capacitor C13 is discharged via the diode D3, the resistor R30, and the transistor Tr5. Note that the discharge time constant at this time is selected to be considerably large.

A capacitor C is connected to the non-inverting input terminal of the operational amplifier OP6.
Sawtooth wave voltage generated at terminal 8 [waveform (5) in Figure 2]
and the dotted waveform (11)], while the terminal voltage of the capacitor C13 (the solid line of the waveform (11) in FIG. 2) is supplied to its inverting input terminal.

Therefore, as shown in waveform (9) in FIG. 2, the output of the operational amplifier OP6 becomes high level only during the time when the terminal voltage of the capacitor C13 becomes larger than the sawtooth wave voltage of the capacitor C8.

Therefore, the output of the operational amplifier OP6 is the capacitor C
As the voltage at the terminal 13 decreases, the pulse waveform has a rising timing that advances. This high level output is supplied to the OR circuit ORI and is superimposed on the half wave output from the transistor Tr8.

The superimposed waveform is applied to the triac TRC1 via the AND circuit AND1, making it conductive. Therefore, the feed motor FM gradually shifts from the initial slow-speed feed using half-wave drive to normal fast-feed using full-wave drive, and when the potential of capacitor C13 becomes sufficiently low, the output of operational amplifier OP6 is almost constant. Since it is a high level,
It becomes completely full wave drive state.

Incidentally, in FIG. 1, the rectifier REF3, the Zener diode ZD1, the transistor Tr6. Tr7, capacitor C
8 and their associated resistors constitute a sawtooth voltage generating circuit, but those skilled in the art will recognize that they may be replaced with other suitable circuit elements and configurations.

Furthermore, the same sawtooth wave signal that is supplied to the non-inverting input terminal of operational amplifier OP7 is supplied to the non-inverting input terminal of operational amplifier OP6, but this signal is supplied to the non-inverting input terminal of operational amplifier OP6.
It may be an intermittent sawtooth wave signal generated only during the low level time of a pulse wave signal corresponding to an AC half wave generated in the collector of No. 8.

A divided voltage by resistors R24 and R25 is supplied as the first overload reference voltage L1 to the non-inverting input terminal of the automatic control operational amplifier OP5 during the C1 full-wave drive. This first overload reference voltage L1 is set to a value smaller than a second overload reference voltage L2 for completely stopping overload, which will be described later, by a predetermined value.

During drilling work on a workpiece, if a large load is applied to the drill motor ED for some reason and the load signal Eed exceeds the first overload reference voltage L1, the operational amplifier OP
5 is inverted to low level, and the output of NAND circuit NAN becomes high level.

= 23- Transistor Tr5 is cut off and with a very short time constant,
Capacitor C13 is charged.

As the terminal voltage of capacitor C13 increases, the time during which operational amplifier OP6 generates a high level output decreases, as can be seen from the above description.

In other words, the duty ratio of the pulse generated from the operational amplifier OP6 decreases, and its rising edge phase is delayed.
Ultimately, pulse generation will be eliminated, so the feed motor FM
The drive current approaches half-wave, and the feed speed of the electric drill decreases.

In this way, during the time when the feed motor FM is full-wave driven, the trigger phase of the triac TRC1 is delayed depending on the load of the drill motor ED.The larger the load is, the smaller the feed speed is. The half-wave drive provides a slow feed, and conversely, the smaller the load, the more advanced the trigger phase of the triac TRCl is, so the feed speed is controlled to be large.

D. Full stop control during overload The divided voltage by resistors R55 and R56 is supplied as the second overload reference voltage L2 to the inverting input terminal of the operational amplifier OP8. The load on the drill motor ED becomes larger than the limit, and the load signal Eed reaches the second overload reference voltage L.
When it exceeds 2, the output of the operational amplifier OP8 is inverted and becomes high level.

When this high level signal is applied to the base of the transistor Tr11 via the AND circuit AND3 and the OR circuits OR2 and OR3, the transistor Tr11 becomes conductive and its collector potential drops to a low level. As a result, relay SSR is deenergized, and both drill motor ED and feed motor FM are stopped.

Generally, a large rush current flows when the motor is started, and the load signal Eed at this time may exceed the second overload reference voltage [2]. It won't happen.

For this purpose, a time constant (integration) circuit consisting of a resistor R58 and a capacitor C11, and an AND circuit AND3 are attached to the output side of the operational amplifier OP8.

At the same time that the power switch PS is set to the "2" position and the motor is started, the capacitor C11 is connected to the resistor R58.
It is charged by the control voltage VCC via. However, since the terminal voltage of the capacitor C11 is less than the scheduled value during the scheduled time after startup, the AND circuit AND3 is closed.

Therefore, even if the load signal Fed at startup becomes excessive and the operational amplifier OP8 produces an output, this output will be
It no longer passes through the AND circuit AND3 and the OR circuits OR2 and OR3 to affect the state of the transistor Tr11.

After the scheduled time has elapsed, the terminal voltage of the capacitor C11 becomes high and the AND circuit AND3 is opened, so that the output of the operational amplifier OP8 is no longer blocked, and normal overload protection of the drill motor ED is performed.

Also, resistor R56 on the inverting input terminal side of operational amplifier OP8
The switch S1 connected to short-circuit is a limit switch that is closed when the electric drill advances toward the workpiece to the limit, regardless of whether the drilling operation is completed or not.

When the switch S1 is closed, the output of the operational amplifier OP8 operates in the same way as in the overload case, and the drill motor E
A complete stop of D and feed motor FM is achieved.

E. Full stop control when drilling is completed When drilling of the workpiece is completed, the drill motor ED is almost in a no-load state, so the load signal Eed suddenly decreases.

As a result, the output of the operational amplifier OP4 becomes low level, the transistor Tr4 becomes conductive, and the capacitor C7 is connected to the diode D1, the resistor R2'l and the transistor Tr4.
is discharged through. The output of the inverter circuit IN2 is inverted to a high level, and this is transmitted to one input of the AND circuit AND2.

At this time, as described above, the capacitor C12 is charged and its terminal voltage is at a high level, so the output of the AND circuit AND2 becomes a high level, and this signal is passed through the OR circuits OR2 and OR3 to the transistor Tr11.
is applied to the base of , making it conductive.

Therefore, the collector of the transistor Tr11 falls to a low level, and the light emitting diode LED6 is turned off.
Relay SSR is disconnected, and both drill motor ED and feed motor [M] stop.

Since the output of the OR circuit OR3 is fed back to its human power, the OR circuit OR3 is self-maintained and its output maintains a high level.

Note that the light emitting diode LED5 connected to the collector-emitter circuit of the transistor R13 is a relay SSR.
This is an indicator light indicating a non-operating state of the drill motor ED and the feed motor FM, that is, a stopped state of the drill motor ED and the feed motor FM, and lights up when the drill motor ED and the feed motor FM are stopped.

The completion of drilling can also be detected by monitoring the differential value of the load signal Eed and detecting that the differential value exceeds the negative predetermined value, so this detection output is sent to the AND circuit A.
It is clear that it may be used instead of the output of ND2.

F, load state display load signal Eed is also supplied to each non-inverting input terminal of the operational amplifiers OP1 to OP3. The operational amplifier OP1
Reference voltages E1 to E3 divided by resistors R4 to R9 are applied to each inverting input terminal of ~OP3.

Now, between the reference voltages E1 to E3, El<22<2
Assuming that there is a relationship of
D1 lights up.

As the load increases step by step, operational amplifier OP2. O
P3 sequentially produces an output, and the light emitting diodes LED2 . L
ED3 are lit in sequence. In this way, by looking at the lighting states of the light emitting diodes LED"1 to LED3, it is possible to know whether the drill motor ED is under a light load, a normal load, or a heavy load.

In the above, an example has been described in which the present invention is implemented by hard logic using a combination of individual logic elements, but as will be apparent to those skilled in the art, the present invention can also be implemented by soft logic (software) using a computer.

(Effects of the Invention) As is clear from the explanations given below, according to the present invention, the following effects are achieved.

(1) At the start of drilling, the feed motor is driven in half-wave, and the feed speed of the electric drill is extremely low, ensuring that it penetrates into the hard parts (black scales) on the surface of the workpiece, resulting in highly accurate drilling. Furthermore, there is no risk of the drilling machine swinging around due to overload.

(2) After drilling the black skin, the drive of the feed motor is gradually switched from half-wave to half-wave, and the feed speed increases, so drilling can be performed at the highest efficiency that matches the performance of the electric drill. I can do it.

(3) Since optimal feed rate control is achieved according to the load of the drill motor, the size (diameter) of the annular cutter can be selected within a wide range.

(4-) During the entire process of drilling work, the drill motor ED
Since the optimum and highest feed rate control corresponding to the load is achieved, the highest work efficiency is achieved without causing the drilling machine to swing around. Therefore, a relatively small drill motor can be used to perform high-load, in other words, large-diameter drilling safely and with high efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a time chart for explaining its operation, and FIG. 3 is a schematic diagram showing the overall configuration of mechanical parts suitable for applying the present invention. The perspective view and FIG. 4 are the right side views thereof. ED...Drill motor, FM...Feed motor, MG
...Electromagnetic magnet 1~, PS...Power switch, R
2O... Rectifier and smoothing device, SSR... Relay, STB
... Constant voltage device, TRC ... Triac agent
Patent attorney Michito Hiraki and 1 other person Fig. 3 r Fig. 4 e G) /39]

Claims (5)

[Claims] (1) A control device for a drilling machine comprising an electric drill separately having a drill motor and a feed control motor connected to an AC power source, and an electromagnetic base for fixing the electric drill to a workpiece, the control device being for feed control. switching means for controlling power supply to the motor; means for detecting a load signal representative of the load current of the drill motor; means for generating a sawtooth wave signal having a frequency twice the frequency of the AC power supply; and the AC power supply. means for generating a first pulse corresponding to a half wave of the signal; and means for generating a second pulse that is synchronized with the sawtooth wave signal and whose duty ratio increases as the load signal decreases; 1. A control device for a drilling machine that can be fixed to a workpiece on an electromagnetic basis, comprising means for controlling the timing of applying an alternating current voltage to a feed control motor according to the logical product of two pulses. (2) A control device for a drilling machine comprising an electric drill separately having a drill motor and a feed control motor connected to an AC power source, and an electromagnetic base for fixing the electric drill to a workpiece, the device for controlling the feed. switching means for controlling power supply to the motor; means for detecting a load signal representative of the load current of the drill motor; means for generating a sawtooth wave signal having a frequency twice the frequency of the AC power supply; and the AC power supply. means for generating a first pulse corresponding to a half wave of the AC power source; means for generating a second pulse that is synchronized with the sawtooth wave signal and whose duty ratio increases as the load signal decreases; and at least one of the AC power sources. means for generating, during the remaining half-wave period, a third pulse whose duty ratio increases as time elapses from the start of the drill motor; an OR circuit for calculating the logical sum of the first and third pulses; and the logic circuit. means for controlling the timing of applying an alternating current voltage to the feed control motor according to the logical product of the sum and the second pulse; 1. A control device for a drilling machine that can be fixed to a workpiece using an electromagnetic base, comprising means for controlling the duty ratio of three pulses to be small. (3) Control of a drilling machine that can be fixed to a workpiece using an electromagnetic base according to claim 2, wherein the first pulse and the third pulse are synchronized with the voltage waveform of an AC power supply. Device. (4) A drilling machine capable of being fixed to a workpiece using an electromagnetic base according to claim 2 or 3, wherein the duty ratio of the third pulse varies between 0 and 1. control device. (5) The duty ratio of the third pulse is controlled by advancing or delaying the rising timing of its leading edge, and is fixed to the workpiece using the electromagnetic base according to claim 4. Possible drilling machine control device.