JP2010036306A - Safety device for electric drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety device for an electric drill capable of protecting a circuit by preventing destruction of an electronic components when a drill of the electric drill comes in contact with a charge section and surely detecting grounding of the drill of the electric drill to operate without having any influence of fluctuation on voltage of a power source. <P>SOLUTION: Voltage between a drill 4a of the electric drill 4 and ground connection G and reference potential are compared by a comparison circuit 7 of operational amplifier IC1 in which a DC stabilized power supply 6 is used as a power supply. When the drill 4a of the electric drill 4 detects that the drill 4a is grounded by coming in contact with piping of electricity, gas, and water service, and the voltage between the drill 4a and the ground connection G becomes designated voltage a buzzer 11 is rumbled by turning on a switching circuit 10 and a ground fault interrupter 5 connected with the power supply of the drill 4a is operated for interrupting. Further, an electronic circuit is protected so as not to apply excessive voltage when the drill 4a comes in contact with a charge section 17 by damaging an electric wire, and the ground fault interrupter 5 is operated for interrupting while the buzzer 11 is rumbled. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a safety device for an electric drill that cuts off the power of the electric drill and issues an alarm when the drill hits a pipe of electricity, gas, water, or the like provided in the building when making a hole in the building with the electric drill. About.

  Conventional safety devices for electric drills detect the ground current between the drill and ground using an electric thyristor, and when drilling holes in a building with an electric drill, piping for electricity, gas, water, etc. When the drill touches the ground, the buzzer sounds when the ground current flows to the photothyristor and turns on, and the earth leakage breaker connected to the power supply of the electric drill shuts off, stopping the operation of the electric drill and Damage has been prevented (see, for example, Patent Document 1).

Japanese Utility Model Publication No.59-183709

  However, the conventional safety device for electric drills breaks down the electronic components that make up the safety device's circuit if the drill touches live parts, such as by accidentally damaging a wire when drilling a building with an electric drill. There was a problem that the safety device stopped functioning. In addition, a voltage stepped down from a power supply voltage of 100 V to 3.3 V by a step-down transformer is applied between the drill and the ground of the electric drill, but when the power supply voltage fluctuates, it is applied between the drill and the ground. The voltage may fluctuate and the photothyristor may not turn on, and the safety device may not work.

  According to the present invention, the voltage between the drill and the ground of the electric drill is detected, and when the voltage between the drill and the ground reaches a predetermined voltage, the switching circuit is turned on and the buzzer is turned on. It is a safety device for electric drills that operates and cuts off the earth leakage breaker connected to the power supply of the electric drill, protecting the electronic circuit when the drill touches the live part, and sounding the buzzer and breaking the earth leakage The device is cut off.

  According to the invention of claim 2, the voltage between the drill and the ground of the electric drill is detected, and when the voltage between the drill and the ground reaches a predetermined voltage, the switching circuit is turned on and the buzzer is sounded. A safety device for an electric drill that interrupts an earth leakage breaker connected to the power source of the electric drill, and compares the voltage between the drill and ground with a reference potential by an operational amplifier comparison circuit that uses a DC stabilized power source as a power source. And the ground contact state of the drill is detected.

  According to the first aspect of the present invention, there is an effect that the circuit can be protected by preventing destruction of the electronic component when the drill of the electric drill comes into contact with the charging unit.

According to the second aspect of the present invention, there is an effect that the safety device operates by reliably detecting that the drill of the electric drill is grounded without being affected by fluctuations in the power supply voltage.
There is an effect.

  The safety device for electric drills compares the voltage between the electric drill and the ground and the reference potential using an operational amplifier comparison circuit that uses a DC stabilized power supply as a power source. The earth leakage breaker connected to the power supply of the electric drill is turned on by turning on the switching circuit and sounding the buzzer when the voltage between the drill and ground reaches the specified voltage. Shut off operation. Moreover, when a drill touches a live part, for example, by damaging an electric wire, the electronic circuit is protected so that an overvoltage is not applied, and a buzzer is sounded and a leakage breaker is cut off.

  A safety device for an electric drill according to a first embodiment of the present invention will be described with reference to the attached drawing of FIG.

  An electric drill safety device 1 includes a power line 3 connected to a commercial power source 2, an earth leakage breaker 5 that connects the primary side to the power line 3, and an electric drill 4 is connected to the secondary side to supply power, A DC stabilized power supply 6 connected to the power supply line 3 to supply a stable DC power supply to each circuit, a voltage between the drill 4a of the electric drill 4 and the ground G is detected, and between the drill 4a of the electric drill 4 and the ground G A comparison circuit 7 for comparing the voltage of the current and a reference potential, an average value circuit 8 for averaging and outputting the output of the comparison circuit 7, and a trigger circuit 9 for outputting a signal to the switching circuit 10 by the output of the average value circuit 8; Charging that outputs a signal to the trigger circuit 9 when the switching circuit 10 that is turned on by the output of the trigger circuit 9, the buzzer 11 that rings when the switching circuit 10 is turned on, and the drill 4 a of the electric drill 4 contact the charging unit 17. A contact detection protection circuit 12, is made and an operation changeover switch 13.

  The electric drill safety device 1 configured in this way supplies power to the electric drill 4 by connecting the power source of the electric drill 4 to the secondary side of the earth leakage breaker 5 and turning on the switch of the earth leakage breaker 5. Is done. Then, the signal line 14 electrically connected to the drill 4a of the electric drill 4 is connected to the connection terminal E of the safety device 1 for the electric drill, the connection terminal F is connected to the ground G, and the operation switch 13 is set to the position A. When the power is turned on, the power can be turned on and used.

  The electric drill safety device 1 with the power turned on supplies a constant voltage to a comparison circuit 7 by a DC stabilized power supply 6 composed of a transistor TR1 and a Zener diode ZD1, and the comparison circuit 7 supplies a resistance R1 and a resistance R1. The divided voltage of the resistor R2 is input to the negative terminal of the operational amplifier IC1 as a reference potential, and is divided by the resistance between the drill 4a of the electric drill 4 and the ground G, the resistance R3, the resistance R4, and the resistance R5, and the positive terminal of the operational amplifier IC1. To be compared and output.

  When the drill 4a hits a grounded pipe 16 such as electricity, gas, water, etc. when a hole is drilled in the building 15 or the like, the voltage between the drill 4a of the electric drill 4 and the ground G changes. When the resistance between the drill 4a of the electric drill 4 and the ground G and the divided voltage divided by the resistance R3 and the resistance R4 and the resistance R5 become higher than the reference potential, a signal is sent from the operational amplifier IC1 of the comparison circuit 7 to the average value circuit 8. Output. The average value circuit 8 averages the signal input from the comparison circuit 7 and outputs the average signal to the trigger circuit 9. In particular, a square waveform output when there is almost no potential difference between the voltage at the plus terminal of the operational amplifier IC 1 and the reference potential. A constant waveform is output.

  The transistor TR2 and the transistor TR3 of the trigger circuit 9 are sequentially turned on by the signal output from the average value circuit 8, and a trigger signal is output to the thyristor SCR1 of the switching circuit 10. When a trigger signal is input to the thyristor SCR1 of the switching circuit 10, the thyristor SCR1 is turned on, the buzzer 11 sounds to notify the user of the abnormality, and a pseudo leakage current flows to the zero-phase current transformer 5a of the leakage breaker 5 Then, the electric circuit is interrupted and the operation of the electric drill 4 is stopped.

  Further, when the drill 4a contacts the charging unit 17 by accidentally damaging the electric wire when making a hole in the building 15 with the electric drill 4, the charging unit contact detection protection circuit 12 is connected via the diode D1 and the resistor R6. When a current flows through the diode of the photocoupler PC and a current flows through the diode of the photocoupler PC, the transistor of the photocoupler PC is turned on, and the transistor TR4 is turned on. When the transistor TR4 is turned on, a current flows through the diode D2, the thyristor SCR2 is turned on, the potential between the resistor R4 and the resistor R5 becomes 0, the positive terminal of the operational amplifier IC1 is protected from overvoltage, and the operational amplifier IC1 is damaged. Can be prevented. Further, when the transistor TR4 is turned on, the thyristor SCR3 is turned on, and the transistor TR5 is turned on. When the transistor TR5 is turned on, a current flows through the diode D3 and the transistors TR2 and TR3 of the trigger circuit 9 are turned on. Therefore, a trigger signal is output from the trigger circuit 9 and the buzzer 11 is turned on by turning on the thyristor SCR1 of the switching circuit 10. It rings and informs the user of an abnormality, and a pseudo leakage current flows through the zero-phase current transformer 5a of the leakage breaker 5 to interrupt the electric circuit and stop the operation of the electric drill 4. Thereby, destruction of an electronic component can be prevented and a circuit can be protected.

  When the operation changeover switch 13 is set to the position B, the electric drill safety device 1 can be turned off. When the operation changeover switch 13 is set to the position C, the buzzer 11 sounds but the earth leakage breaker 5 does not operate when an abnormality occurs. Can be.

It is a circuit diagram of the safety device for electric drills which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Safety device for electric drills 2 Commercial power supply 3 Power supply line 4 Electric drill 4a Drill 5 Earth leakage breaker 5a Zero phase current transformer 6 DC stabilized power supply 7 Comparison circuit 8 Average value circuit 9 Trigger circuit 10 Switching circuit 11 Buzzer 12 Charging part Contact detection protection circuit 13 Operation switch 14 Charging part 15 Building 16 Piping 17 Charging part

Claims (2)

  The voltage between the drill and the ground of the electric drill is detected. When the voltage between the drill and the ground reaches a predetermined voltage, the switching circuit is turned on to sound the buzzer, and the power source of the electric drill is connected. A safety device for an electric drill for interrupting an earth leakage breaker, wherein the electronic circuit is protected when the drill touches a charged part, and the buzzer sounds and the earth leakage breaker is interrupted. Safety device for electric drills.   The voltage between the drill and the ground of the electric drill is detected. When the voltage between the drill and the ground reaches a predetermined voltage, the switching circuit is turned on to sound the buzzer, and the power source of the electric drill is connected. A safety device for an electric drill for interrupting an earth leakage circuit breaker, comprising: comparing a voltage between a drill of the electric drill and the ground and a reference potential by a comparison circuit of an operational amplifier using a DC stabilized power supply as a power source; A safety device for an electric drill, characterized by detecting the grounding state of the electric drill.

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