JPS61131807A - Drilling machine - Google Patents

Abstract

PURPOSE:To prevent a ring cutter from being broken by providing a drilling machine having the automatic feed mechanism for an electric drill with oscillating circuits for intermittently stopping a feed motor by detecting the signals correspondingto the electrical current conducting through a drill motor by the use of a detecting circuit. CONSTITUTION:A drill machine is provided with a frame 1 having a fixing means to a workface, an electric frill 3 having a drill motor 3M, and a feed motor 4. In addition, this drilling machine is provided with an oscillating circuit 58 for intermittently stopping the feed motor 4 and a first detecting circuit 60 for detecting the signals corresponding to the electric current conducting through the drill motor 3M, for stopping the feed motor 4 prior to the operation of the oscillating circuit 58 when the signals exceed a first threshold value, and for releasing the stopping of the motor 4 when the above-mentioned signals do not exceed the first threshold value. And the drilling machine is also provided with a second detecting circuit 70 to stop the drill motor when the signals exceed a second threshold value set at higher value than the first threshold value.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drilling machine, and particularly to a drilling machine having an automatic feeding device for an electric drill.

(Prior Art) A drilling machine is equipped with a means for fixing it to a workpiece, such as an electromagnetic base, at its lower part, and an electric drill at its front. There may be cases where

As is well known, when performing drilling work using an annular cutter, the cutting performance is superior to that when using a twist drill. There is a risk that a large load will be applied to the annular cutter, which may damage the cutting edge of 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, only extremely skilled workers are able to recognize the magnitude of the load, in other words, to discern whether an appropriate load or a large load is being applied to the blade of the annular cutter. Therefore, if the drilling machine is operated by a beginner who is not familiar with its handling, there is an extremely high risk that the aforementioned annular cutting tool will be damaged or the electric drill will be burnt out.

Further, it is necessary 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 switching of the annular cutter.

However, with conventional drilling machines, the operator has to turn off the power switch of the drilling machine after completing the drilling work.

Therefore, it is difficult for the worker to use the flowers, and for this reason, the workability is also not very good.

In order to solve each of the above-mentioned drawbacks, the present inventors.

We are conducting various research and development and have already applied for patents.

The invention related to the above patent application is patent application No. 56-186473.
It is disclosed in No. IB and No. 57-23741 No. II.

The invention described in the specification of Japanese Patent Application No. 57-23741 is equipped with a feed motor for advancing the electric drill toward the workpiece, and the control circuit of the electric drill is configured to control the magnitude of the load of the electric drill. , a detection section is provided that detects a change in voltage based on a change in the current flowing therein, and when the detection section detects a load at the level set in the first stage, the feeding of the electric drill is automatically stopped. Then, when a reduction in the load is detected, the feed of the electric drill is restarted, and when an excessive load is detected in the second stage, the rotation of the electric drill and the feed of the electric drill are restarted. The present invention is characterized in that the rotation of the electric drill and the feeding of the electric drill are automatically stopped when drilling is completed.

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

(1) When performing drilling work using an annular cutter, even if the load can be detected, a very large load may sometimes be applied to the annular cutter. This impact load is thought to be induced, for example, by a built-up cutting edge formed on the blade portion of the annular cutter, or by poor evacuation of chips formed during drilling.

If the annular cutter is relatively large, the impact load will be absorbed by the annular cutter, but if the annular cutter is small, the impact load will be absorbed by the annular cutter before the feed of the electric drill of the drilling machine or the rotation of the electric drill is stopped. Moreover, the annular cutter may be damaged.

(2) When performing drilling work, a thrust force is naturally applied to the electric drill.The thrust force is
This occurs even when drilling is performed under optimal conditions.

However, since the drilling machine is fixed to the workpiece by electromagnetic force due to the electromagnetic base leaking from the bottom of the drilling machine, the thrust force creates an extremely small gap between the electromagnetic base and the workpiece. However, there is a risk that gaps may be formed.

The gap makes it impossible for the main shaft of the electric drill to maintain a predetermined angle (usually perpendicular) to the work surface. In other words, the annular cutter is tilted from the perpendicular to the work surface, resulting in a distorted hole or a hole not being formed perpendicular to the work surface. moreover,
At this time, the annular cutter becomes in a so-called uneven state, and the possibility of breakage of the annular cutter increases.

Note that once the gap is formed, it will not disappear while the feed motor of the electric drill is operating, so the load on the annular cutter will be lower than the load at the set level in the first stage described above. If the size is also small, there is a strong possibility that the above-mentioned problem will occur.

(a) In the drilling machines described in each of the above-mentioned specifications, in order to prevent the detection unit from malfunctioning due to the large current generated when starting the drill motor, the first and second stage set level detection means in the detection unit are (constant voltage diode) is connected to a delay circuit consisting of a resistor and a capacitor. However, with this configuration, there is a delay in the response of the setting level detection in the first and second stages, and the drill motor and feed motor The disadvantage is that the timing of stopping is delayed.

(4) In this case, if the time constant of the delay circuit is increased, the breakdown voltage of the constant voltage diode cannot be reduced very much. In other words, the first and second
Since the setting level of the step cannot be made very small, even if a relatively large load is applied to the annular cutting tool of the drilling machine, the feeding of the electric drill or the rotation of the annular cutting tool cannot be stopped. Therefore, the life of the electric drill and the annular cutter cannot be made very long.

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

(Means and Effects for Solving the Problems) In order to solve the above problems, the present invention provides that when the signal corresponding to the current flowing through the drill motor exceeds a first threshold, the feed motor is activated. a first sensing circuit for stopping rotation, and a second sensing circuit for further stopping rotation of the drill motor when said signal exceeds a second threshold; A measure is taken to provide an oscillation circuit that intermittently stops the feed motor when the feed motor is below a threshold, thereby facilitating the removal of built-up edges formed on the tool and evacuation of chips, and , Even if a gap occurs between the electromagnetic base and the work surface, the electromagnetic base and the work surface can be brought into close contact immediately;
This is characterized by the effect that the angle between the tool and the work surface can always be corrected to a predetermined angle.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic perspective view of an embodiment of the present invention, and FIG. 3 is a right side view of the embodiment.

In each figure, 1 is a frame, 2 is an electromagnetic base attached to the bottom of the frame 1, 3 is an electric drill installed on the front of the frame 1 so that it can be raised and lowered either manually or electrically, and 4 is an electric drill 3. The feed motor 5 is an annular cutting tool attached to the arbor 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 35 (described later with reference to FIG. 4).

Reference numeral 40 denotes an operation handle for operating the starting switch 6, which moves in two stages and connects the switch's three contacts 6A,
Inject 68.6G in the prescribed order.

The operating circuit constituting the main part of the present invention includes the frame 1
Built-in.

Next, an outline of the present invention will be explained using a block diagram.

FIG. 1 is a schematic block diagram illustrating the functionality of the present invention. In FIG. 1, the same reference numerals as in FIGS. 2 and 3 represent the same or equivalent parts.

In FIG. 1, the starting switch 6 of the drilling machine has contacts 6A, 6B and 6C.

When the start switch 6 is operated, contacts 6A and 6C first close, and then contacts 6B and 6 close.
C is configured to close.

An AC power source 90 is connected to the contact 6C.

An electromagnet (not shown) in the electromagnetic pace 2 is connected to the contact point 6A.
It is connected to the.

The drill motor 3M connects the contact 6 via the second relay 12.
Connected to B.

The feed motor 4 is connected to the contact point 6B via the first relay 23 and the manual switch 14 in series.

The oscillation circuit 58 is, for example, a rectangular wave generation circuit, and the oscillation circuit 58 is a rectangular wave generation circuit, and the oscillation circuit 58 is a rectangular wave generation circuit.
Turn 3 on/off.

The first and second detection circuits 60, 70 are connected to the drill motor 3M, and detect the current flowing through the drill motor 3M.

The first detection circuit 60 is configured such that a signal corresponding to the current flowing through the drill motor 3M is a preset first detection circuit.
If the threshold value is exceeded, the contact of the first relay 23 is opened in priority to the operation of the oscillation circuit 58.

The second detection circuit 70 further detects a contact point of the second relay 12 when the signal exceeds a second threshold value that is preset to a value higher than the first threshold value. to open.

First, when the operating lever 40 is operated in the first step to turn on the starting switch 6 and the contacts 6A and 6C are closed, an attractive force is generated in the electromagnetic base 2. This fixes the drilling machine to the workpiece.

Next, when contacts 6B and 6C close, drill motor 3M and feed motor 4 rotate. At this time, the punch 41 (not described in detail) uses the spring 42 which has stored energy in advance.
It descends instantaneously due to the force of the explosion and pierces the surface of the workpiece.

However, even if the feed motor 4 rotates, the drill 3 does not immediately start descending, and the drill 3 is first lowered by turning the manual lift operation handle 39 to start drilling, and then the annular cutter 5 starts drilling. Once started, automatic feeding of the electric drill 3 is started by engaging a clutch, which will not be described in detail.

When automatic feeding of the electric drill 3 is started, the oscillation circuit 58
From there, a control signal for the first relay 23 is intermittently output, and the first relay 23 is turned on/off. As a result, since the feed motor 4 repeats rotation/stop at scheduled time intervals, the feeding operation of the annular cutter 5 is also performed intermittently.

The intermittent feeding operation (hereinafter referred to as step feeding) of the electric drill 3, i.e., the intermittent stop of the feeding operation of the electric drill 3, allows the ejection of chips formed during drilling and the removal of the annular cutter 5. The built-up cutting edge formed on the blade portion can be easily removed. Thereby, the risk of applying an impact load to the annular cutter 5 is reduced, and the life of the annular cutter 5 is extended.

Further, even if a gap occurs between the electromagnetic base 2 and the workpiece during the feeding operation of the electric drill 3, the intermittent stop of the feeding allows the electromagnetic base 2 and the workpiece to come into good contact again. I can do it. In other words, even if the angle formed between the work surface and the annular cutter 5 deviates from a predetermined angle during the feed operation of the electric drill 3, the angle is adjusted to the predetermined angle each time the feed is stopped intermittently. It will be corrected.

Therefore, good holes without deformation or inclination can be formed.

Now, if the load applied to the annular cutter 5 becomes large despite the step feed of the electric drill 3, and the signal corresponding to the current flowing to the drill motor 3M exceeds a preset first threshold value. , first detection circuit 60
opens the contact of the first relay 23 regardless of the operation of the oscillation circuit 58. As a result, the feed motor 4 is stopped, and the feeding of the electric drill 3 is stopped.

If the stoppage of the feed motor 4 causes the signal to become lower than a first threshold, the continuous stoppage of the feed motor 4 is canceled. Then, step feed of the electric drill 3 is performed again by the operation of the oscillation circuit 58.

Even after the feed motor 4 is forcibly stopped by the first detection circuit 60, the drill motor 3M remains unchanged.

If the flowing current does not decrease and the signal exceeds a second threshold, which is preset to a value higher than the first threshold, the second sensing circuit 70 activates the second relay. 12
Open the contacts. As a result, not only the electric drill 3 is fed but also the rotation of the annular cutter 5 is stopped.

In addition, when a shockingly large load is applied to the rotating annular cutter 5 under a light load and the signal exceeds the second threshold, the electric drill 3 is fed and the annular cutter 5 is stopped in the same manner as described above. rotation stops.

In this case, on the one hand, the electric drill 3 is raised by switching a clutch (not described in detail) from automatic to manual and operating the manual lifting operation handle 39, and on the other hand, the operating lever 40 is moved to the first position.
Return to the stage position, open 6B, and turn off the power to the drive motor 3A and feed motor 4 of the electric drill 3 to eliminate the cause of the overload. Note that when 6B is opened, the output signals of the first and second detection circuits 60 and 70 are canceled. To restart the drilling operation, as described above, after removing the cause of the high load on the annular cutter 5, for example, after discharging chips, etc., the operation lever 40 is activated. By operating to the second stage position and closing the contact point 6B again, the drill motor 3M and the feed motor 4 are started, and the same operations as at the start of drilling are performed to restart the drilling work of the drilling rock.

Next, an example of a specific circuit diagram of the present invention will be explained.

FIG. 4 is a specific circuit diagram of an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 1 represent the same or equivalent parts.

In FIG. 4, an electromagnet 83 and a pilot lamp 8
4 is connected to eight input terminals and a contact point 6A of the starting switch 6.

The contacts of the drill motor 3M and the second relay 12 are connected in series, and are connected to the eight input terminals and the contact 6B of the start switch 6.

The second relay 12 is a solid state relay (switching element) that becomes conductive when a predetermined voltage is applied to its control terminal. The control terminal is connected to an anode of a silicon-controlled rectifying element 31, which will be described later.

The current transformer 16 is arranged to detect the current flowing through the drill motor 3M.

The manual switch 14 is a switch for switching between manual feeding and automatic feeding of the electric drill 3. When automatic feeding by the feed motor 4 is performed, this switch is turned on, and when manual feeding is performed, this switch is turned off.

Manual switch 14. feed motor 41 phase control circuit 34;
A contact 24B1 of the first relay 23, an emergency warning lamp 33, and a contact 24A of the first relay 23, which will be described later, are also connected in series as shown in the figure, and furthermore, the input terminal 89 and the start switch 6 are connected in series. Contact 6
Connected to B. The contact 24B is a normally closed contact, 2
4A is a normally open contact.

Further, the input terminal of the transformer 81 is also connected to the input terminal 89 and the contact 6B of the starting switch 6. An output terminal of the transformer 81 is connected to an input terminal of a rectifier constant voltage circuit 82 . As shown in the figure, the output terminal of the rectifying constant voltage circuit 82 includes an integrating circuit 74, voltage dividing resistors 75 and 76 connected in series, a resistor 77 and a silicon v-controlled rectifying element 31, and a voltage dividing resistor 65 and 66, an oscillation circuit 58, and the first relay 23 are connected.

The inverting input terminal 71A of the operational amplifier 71 is connected to the resistor 75.
and 76, and its non-inverting input terminal 71B is connected to the output line 101 of the current transformer 16. One input terminal 72.8 of the second AND circuit 72 is connected to the output terminal of the operational amplifier 71, and the other terminal 72.DELTA. is connected to the output line of the integration circuit 74. One of the input terminals of the OR circuit 73 is connected to the output terminal of the second AND circuit 72, and the other terminal is connected to the output terminal of the second AND circuit 72 via the limit switch 35.
It is connected to the positive output terminal of the rectifier constant voltage circuit 82. The output terminal of the OR circuit 73 is connected to the gate of the silicon controlled rectifying element 31.

The anode of the silicon-controlled rectifying element 31 is connected to the control terminal of the second relay 12, as described above.

A non-inverting input terminal 61A of the operational amplifier 61 is connected to the resistor 6.
5 and 66, and its inverting input terminal 61B is connected to the output line 101 of the current transformer 16.
It is connected to the.

One of the input terminals of the first AND circuit 62 is connected to the output terminal of the operational amplifier 61, and the other terminal is connected to the anode of the silicon-controlled rectifying element 31.

Further, one of the input terminals of the NAND circuit 520 is connected to the output terminal of the first AND circuit 62, and the other is connected to the output terminal of the oscillation circuit 58. The output terminal of the NAND circuit 52 is connected to the control terminal of the first relay 23.
#Connected to J@child.

Note that a voltage is generated on the output line 101 of the current transformer 16 in accordance with the current flowing through the drill motor 3M.

Said resistance 65.66.75. and 76 are selected such that the potential difference at connection points A and B is the first and second thresholds.

Now, the operation of the circuit having the above configuration will be explained next.

First, when the AC power source 90 is connected to the input terminals 88 and 89 and the operating lever 40 is operated in the first step to turn on the start switch 6, the contacts 6A and 6C are first connected.

Then, the electromagnet 83 and the pilot lamp 84 are energized, and the perforation rock is fixed to the work surface. At this time, the punch 41 drops instantaneously due to the elastic force of the spring 42, which has stored energy in advance, and hits the surface of the workpiece.

Next, when the operating lever 40 is operated by a second step and the contact 6B contacts the contact 6C, a constant DC voltage is output from the rectifying constant voltage circuit 82.

Here, a potential determined by the resistors 75 and 76 is generated at the inverting input terminal 71A of the operational amplifier 71, but no potential is generated at the non-inverting input terminal 71B, so the output of the operational amplifier 71 is OII. It is.

Therefore, since the output of the OR circuit 73 is also "O++," the silicon-controlled rectifier 31 is not conductive, and here, the point C
Then, a voltage sufficient to turn on the second relay 12 is generated. As a result, the drill motor 3M and the feed motor 4 rotate.

As is well known, when the drill motor 3M is started, a large current flows through the drill motor 3M, so that a potential corresponding to the large current is also generated in the output line 101 of the current transformer 16.

In this case, the voltage applied to the non-inverting input terminal 71B is
The voltage applied to the inverting input terminal 71A may exceed the voltage applied to the inverting input terminal 71A, so that the output of the operational amplifier 71 becomes "1".
” However, the integration circuit 74 does not output when a large current is generated at the time of starting the drill motor 3M.

In other words, the time constant is determined so that the output signal is not supplied to the input terminal 72A until the current value flowing through the drill motor 3M decreases at startup and the output of the operational amplifier 71 becomes O''. Therefore, the output of the second AND circuit 72 is "0" regardless of the large current.

Therefore, no trigger signal is supplied to the gate of the silicon-controlled rectifying element 31.

Now, when the current value of the drill motor 3M becomes smaller,
The potential at the inverting input terminal 61B of the operational amplifier 61 is
Since the potential is smaller than the potential at the non-inverting input terminal 61A, the output of the operational amplifier 61 becomes "'1". here,
Since the silicon controlled rectifying element 31 is not conducting, the point C
The potential at, ie, the other input of the first AND circuit 62, is high, so that the output of the first AND circuit 62 is 1°'. Therefore, the output of the oscillation circuit 58 turns the first relay 23 on and off at predetermined time intervals, thereby opening and closing the contacts 24A and 24B of the first relay 23.

Here, the electric drill 3 is lowered by adjusting the manual lift operation handle 39 to the same size, and the cutting edge of the annular cutter starts cutting the surface of the workpiece in an annular shape. After some cutting has been performed and normal cutting is confirmed by the annular cutter, a clutch (not shown) attached to the feed motor 4 is engaged to change manual feed by the operating handle 39 to automatic feed by the feed motor 4. After switching, the feed motor 4 rotates intermittently in response to the operation of the first relay 23, and the electric drill 3 is fed step by step. Note that the speed of the feed motor 4 is adjusted by a phase control circuit 34.

Next, when a relatively large load is applied to the annular cutter 5 during cutting work, the current flowing through the drill motor 3M increases, and the potential of the output line 101 changes to the potential at the point A (the first threshold). Therefore, the output of the operational amplifier 61 is OI! Then, the output of the first AND circuit 62 also becomes "O".

Therefore, even though the oscillation circuit 58 supplies an output signal to the NAND circuit 52, the NAND circuit 52
Since this always outputs "1", the first relay 23 does not operate intermittently and opens the contact 24B continuously.This allows the feed motor 4 to rotate continuously. 7°, the step feed of the electric drill 3 is stopped, and the load on the annular cutter 5 is reduced.
When the potential of the output line 101 becomes lower than the potential of point A again, the output of the operational amplifier 61 becomes "1", and the step feed of the electric drill 3 is restarted.

Next, even if the step feed is stopped, the load on the annular cutter 5 is not reduced and the potential of the output line 101 becomes higher than the potential of point B (second threshold), the operational amplifier 71 outputs ``1''.

As a result, the AND circuit 72 of M2 outputs "1",
The voltage is applied to the gate of the silicon-controlled rectifying element 31 through this °1"1" output circuit 73. Therefore, the silicon-controlled rectifying element 31 becomes conductive, and the potential at point C decreases.

Due to the drop in potential at the point C, the second relay 12
is turned off, and the rotation of the drill motor 3M and feed motor 4 is stopped.

At this time, the clutch attached to the feed motor 4 is disengaged to switch the feed from automatic to manual, and the manual lifting operation handle 39 is operated to raise the electric drill 3. In addition, the operation lever 40 is returned to the first stage position, the contact 6B of the start switch 6 is opened, and the drive motor 3A and feed motor 4 of the electric drill 3 are turned off to perform operations such as removing chips. Eliminate the cause of overload. Note that when the contact 6B is opened, the output voltage of the rectifier constant voltage circuit 82 disappears, so the 7 nodes of the silicon controlled rectifier 31
The voltage applied between the cathodes disappears, returning the silicon-controlled rectifying element 31 to the OFF state.

That is, the outputs of the first detection circuit 60 and the second detection circuit 70 become "OII".

After removing the cause of the overload on the annular cutter 5,
When the three manual lift operation handles are returned to the second stage position and the contact point 6B is brought into contact with the contact point 6C, the drill motor 3M and the feed motor 4 start rotating again.

Next, the electric drill 3 is lowered by operating the manual lift operation handle 39, and the cutting edge of the annular cutter 5 is lowered to the original cutting location. At this time, the clutch is engaged, the feed is switched from manual to automatic, the feed motor 4 performs automatic feed, and the annular cutter 5 performs the drilling operation under a torque below a predetermined level. Eventually, the tip of the annular cutter 5 comes out to the underside of the workpiece, and when the drilling operation is completed, a screw is inserted into the inner surface of the slide plate 36 (Fig. 3), which has been moving along with the electric drill 3. Switch operation plate 37 (third
In Figure), the limit switch 35 is operated and the contact of the switch is closed.

As a result, a gate signal is supplied to the silicon-controlled rectifying element 31, and the potential at point C decreases.

Therefore, the second relay 12 is turned off and the first
Since the relay 23 is turned on continuously, the drill motor 3M of the electric drill 3 and the feed motor 4 of the electric drill 3 are automatically stopped, as in the case where the load of the electric drill 3 exceeds a predetermined value. do.

When the drilling machine is to be moved to another location after the drilling operation is completed, the manual lifting operation handle 39 (FIG. 3) is operated to raise the electric drill 3 and move the annular cutter 5 out of the hole. next,
Operate the operating lever 40 to return it to the base point and start switch 6
All contacts are turned off, the electromagnetic base 2 attached to the lower part of the frame 1 is demagnetized, the bonder 41 is raised against the single force of the spring 42, and the punch 41 is kept at its upper limit position.

This allows the drilling machine to be freely moved to the next drilling position.

Now, in one embodiment of the present invention as described above, point A determined by resistors 65, 66.75, and 76
The potentials of and B determine the timing to stop the rotation of the feed motor 4 and drill motor 3M of the drilling machine. Therefore, it is desirable that the potential be adjusted to an optimal value determined by the type of tools attached to the electric drill 3 and their diameters. The adjustment can be easily performed, for example, by using variable resistors as each of the resistors.

Furthermore, the drilling work can be performed efficiently by adjusting the on/off interval of the step feed of the electric drill 3, that is, the oscillation cycle and duty ratio of the oscillation circuit 58, depending on the type of tools or their diameters. can be

Furthermore, in the above description, means for intermittently stopping the feed motor 4 by the output of the oscillation circuit 58, means for stopping the feed motor 4 by the output of the first detection circuit 60, and a second detection circuit are described. Although the means for stopping the feed motor 4 by the output of 70 are both the first relay 23, the means need not be used in common, and may be different relay circuits.

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

(1) a first detection circuit that stops rotation of the feed motor when a signal corresponding to a current flowing through the drill motor exceeds a first threshold; and a first detection circuit that stops rotation of the feed motor when a signal corresponding to a current flowing through the drill motor exceeds a second threshold; In addition to a second detection circuit that roughly stops the rotation of the drill motor when the drill motor is rotated, an oscillation circuit that intermittently stops the feed motor when the signal is below a first threshold is provided. Therefore, it becomes easier to remove the built-up cutting edge formed on the tool attached to the main shaft of the electric drill and to eject chips formed during drilling. Therefore, the probability that an impact load will be applied to the tool is reduced, and the life of the tool is extended.

In addition, since the degree to which the feed motor is stopped due to overload is reduced, work efficiency can be increased as a result.

(21 Even if a gap is created between the electromagnetic base and the workpiece due to the reaction force generated in the thrust direction of the electric drill during drilling,
When the feed motor stops, the electromagnetic base and the workpiece can immediately come into close contact again. therefore,
Since the tool can always advance at a predetermined angle with respect to the work surface, it is possible to form a good hole without deformation or deviation.

(3) Furthermore, if a limit switch is provided that stops the drill motor and feed motor when the electric drill moves a predetermined distance, the drilling operation by the drilling machine can be performed extremely safely, and the operation can be performed more safely. Furthermore, the power consumption of the drilling machine can be suppressed as much as possible.

(4) A delay circuit for preventing malfunction of the silicon-controlled rectifying element due to the starting current of the drill motor is configured using an integrating circuit and a second AND circuit, and the potential generated in the output line of the current transformer; When comparing the reference voltage at point B and using the logical product of the comparison result and the output of the integrating circuit as the gate signal of the silicon-controlled rectifier, the delay circuit has no effect on the operation of the first and second relays. Therefore, the response of the first and second relays can be made faster.

(5) When detecting an overload of an electric drill by comparing the potential generated in the output line of the current transformer with a preset reference voltage (i.e., the voltage at points A and B), the drill motor The first and second threshold values, which serve as standards for stopping the rotation of the feed motor, can be set to arbitrary values.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram showing the functions of the present invention. FIG. 2 is a schematic perspective view of one embodiment of the present invention, and FIG.
The right side view of the figure and FIG. 4 are specific circuit diagrams of one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Frame, 2... Electromagnetic base, 3... Electric drill, 3M... Drill motor, 4... Feed motor, 5... Annular cutter, 6... Starting switch, 12...・
・Second relay, 23...First relay, 35...
Limit switch, 37... Switch operation board, 58...
...Oscillation circuit, 60...First detection circuit, 70...
Second detection circuit

Claims (2)

[Claims] (1) A drilling machine comprising a frame having means for fixing to a work surface, an electric drill having a drill motor, and a feed motor fixed to the frame and advancing the electric drill in the direction of the work surface, an oscillation circuit that intermittently stops the feed motor; and a signal corresponding to the current flowing through the drill motor; and when the signal exceeds a first threshold, priority is given to the operation of the oscillation circuit. , stopping the feed motor when the signal falls below the first threshold without reaching a second threshold set higher than the first threshold; 1. A drilling machine comprising: a first detection circuit that releases the drill motor; and a second detection circuit that stops the drill motor when the signal exceeds the second threshold. (2) a frame having means for fixing it to the work surface; an electric drill having a drill motor; a feed motor fixed to the frame and advancing the electric drill in the direction of the work surface; and a current flowing through the drill motor. detecting a corresponding signal, and stopping the feed motor when the signal exceeds a first threshold; and a second threshold, wherein the signal is set higher than the first threshold; a first sensing circuit that releases the stop when the signal falls below the first threshold without reaching a value; and a first sensing circuit that releases the stop when the signal exceeds the second threshold; a second detection circuit for stopping the second detection circuit, the second detection circuit comparing the second threshold value and the signal;
a comparator that generates an output depending on the threshold value of the signal and the magnitude of the signal; means for stopping the drill motor based on the output of the comparator; and a means for blocking the output of the drilling machine.