JP2021014002A - Electric tool with safety device and safety device for electric tool - Google Patents

Abstract

To provide an electric tool with a safety device and a safety device for an electric tool, which forcibly cuts off a power supply itself when kick back occurs, can sufficiently ensure the safety of cutting work and the like, and can be easily and inexpensively applied to an existing electric tool.SOLUTION: An electric tool with a safety device includes a motor that is arranged in a housing and is installed with a tool on a rotary shaft thereof, a power supply switch connected to the motor, and a safety device that is connected between the power supply switch and a motor power supply such as an electric outlet, and can cut off power supply from the motor power supply to the motor when detecting the overcurrent of the motor. The safety device is integrated with a plug provided at a tip end of a power supply cord.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electric tool with a safety device such as an electric circular saw used when cutting a material to be cut such as wood or an iron plate, and a safety device for the electric tool.

Conventionally, as an electric circular saw as an electric tool, a type (referred to as an AC power source type) using a single-phase 100 V AC power source as a drive source thereof has become widespread. In such an electric circular saw, for example, an AC100V motor is arranged in the hanging, the plug of the power cord connected to the motor is connected to the AC100V outlet, and the power switch provided on the handle portion is turned on. Various types of materials to be cut are cut by rotating, for example, a tip saw as a rotary blade (cutting tool) mounted on the rotating shaft of a motor at a predetermined rotation speed. As a publication relating to an electric circular saw, for example, Patent Document 1 is available.

Japanese Unexamined Patent Publication No. 6-278101

However, in such an electric circular saw, when cutting the material to be cut, both sides of the rotary blade are tightened by the material to be cut due to distortion or bending of the material to be cut, and the cutting operator hurriedly pulls out the saw. If this is done, kickback may occur and the circular saw itself may be flipped up toward the operator, resulting in inferior safety in the cutting operation. In particular, the number of accidents caused by kickback has increased in recent years, and the actual situation is that safety measures for electric circular saws, etc., including those currently in use, are desired.

The present invention has been made in view of such circumstances, and an object of the present invention is that the power supply itself can be forcibly shut off when a kickback occurs to ensure sufficient safety during cutting work, or an existing one can be used. It is an object of the present invention to provide a power tool with a safety device and a safety device for the power tool, which can be easily and inexpensively applied to the power tool.

In order to achieve such an object, the invention according to claim 1 of the present invention includes a motor arranged in a housing and a tool mounted on a rotating shaft thereof, a power switch connected to the motor, and the power switch. It is characterized by comprising a safety device which is connected between the motor power supply and a motor power supply such as an outlet and can cut off the power supply from the motor power supply to the motor when an overcurrent of the motor is detected.

Further, according to the second aspect of the present invention, the safety device comprises an overcurrent detecting means for detecting an overcurrent by the motor, a reference value setting means capable of setting a predetermined reference value, and a power supply line for the motor. The power supply cutoff means connected to the motor, the power cutoff means is operated based on the overcurrent value detected by the overcurrent detecting means and the reference value set by the reference value setting means, and the power supplied to the motor is supplied. It is characterized by having a control means for blocking.

Further, in the invention according to claim 3, the motor is an AC motor, the motor is connected to an AC power source as the motor power source via a power cord, and the safety device is attached to an AC plug of the power cord. It is characterized in that it is arranged. At this time, it is preferable that the safety device is integrated with the AC plug as in the invention of claim 4.

Further, the invention according to claim 5 includes an outlet provided on one surface of the insulating cover to which a plug of an electric tool can be connected, and a plug provided on the other surface of the insulating cover and connectable to an outlet for a motor power supply. Connected to the overcurrent detecting means for detecting the overcurrent of the power supply line formed between the outlet and the plug, which is provided in the insulating cover, the reference value setting means which can set a predetermined reference value, and the power supply line. The power cutoff means is operated based on the overcurrent value detected by the power cutoff means and the overcurrent value set by the reference value setting means and the reference value set by the reference value setting means to shut off the power supply to the motor. It is characterized by comprising a control means.

Further, the invention according to claim 6 is provided with a notification means capable of notifying the cutoff state of the power cutoff means and a reset means for resetting the cutoff state of the power cutoff means in the insulating cover. It is characterized by.

According to the invention of claim 1 of the present invention, a safety device is connected between the power switch and the motor power supply and can cut off the power supply from the motor power supply to the motor when an overcurrent of the motor is detected. Therefore, the motor power supply itself can be forcibly shut off based on the overcurrent when kickback occurs, and the motor or the like can be stopped immediately, and the safety at the time of cutting work can be ensured by the inexpensive configuration.

Further, according to the invention of claim 2, in addition to the effect of the invention of claim 1, the safety device detects by an overcurrent detecting means, a reference value setting means, a power cutoff means, and an overcurrent detecting means. Since it has a control means for shutting off the power supplied to the motor by operating the power cutoff means based on the overcurrent value and the reference value set by the reference value setting means, the overcurrent due to kickback or the like can be reliably detected. The motor and the like can be reliably shut off by the power cutoff means, and sufficient safety during cutting work can be ensured.

Further, according to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, the motor is an AC motor, and the motor is connected to an AC power source as a motor power source via a power cord. In addition, since a safety device is provided on the AC plug of the power cord, it can be reliably and easily applied as a kickback countermeasure for an AC power type electric tool, and its safety can be sufficiently ensured.

Further, according to the invention of claim 4, in addition to the effect of the invention of claim 3, since the safety device is integrated with the AC plug, the safety device can be installed simply by inserting the AC plug into the outlet. It is possible to obtain a power tool with a safety device that can be used and is excellent in usability.

Further, according to the invention of claim 5, the insulating cover is provided with an outlet to which a plug of an electric tool can be connected and a plug to be connected to an outlet for a motor power supply, and an overcurrent detecting means is provided in the insulating cover. Control to operate the power cutoff means to cut off the current supplied to the motor based on the overcurrent value detected by the reference value setting means, the power cutoff means, and the overcurrent detecting means and the reference value set by the reference value setting means. Since the means is provided, the power supply itself can be forcibly shut off when kickback occurs and the motor etc. can be stopped immediately, sufficient safety during cutting work can be ensured, and application to existing electric tools is easy and inexpensive. Can be done.

Further, according to the invention of claim 6, in addition to the effect of the invention of claim 5, since the notification means and the reset means are provided in the insulating cover, by operating these in a predetermined manner. , The activated power cutoff circuit can be safely restored (reset), and the safety of the cutting operation can be ensured more reliably.

A perspective view showing an embodiment of an electric circular saw with a safety device according to the present invention. Block configuration diagram showing an example of the safety device Explanatory drawing showing an example of the operation of the safety device Flow chart showing an example of the same operation Schematic diagram showing an example of a safety device for an electric circular saw according to the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.
1 to 4 show an embodiment of an electric circular saw as an electric tool with a safety device according to the present invention. As shown in FIG. 1, the electric circular saw 1 is attached to a housing 2, a motor 3 disposed in the housing 2, and a rotating shaft of the motor 3, and both sides thereof are covered with protective covers as a tool. It is provided with a rotary blade 4 made of a tip saw or the like, a handle 5 provided on one end side of the hanging 2, a power switch 6 provided on a grip portion of the handle 5, and the like.

Further, the power supply switch 6 is connected to the motor 3 with a cable (not shown), and one end of the power cord 7 pulled out from the lower end portion of the housing 2 is connected in the housing 2. A safety device 10 having an insulating cover 11 and a plug 12 is integrally arranged at the tip of the other end of the power cord 7. As the motor 3, for example, an AC motor driven by a single-phase AC100V is used, and an AC power cord having a predetermined length is also used for the power cord 7, whereby the electric round saw 1 is supplied with an AC power supply (single-phase 100V). ) Type.

As shown in FIG. 2, the safety device 10 includes a power cutoff circuit 14 including a breaker, a relay, and the like connected in series to a power supply line 13 arranged in the insulating cover 11, and the power supply line. An overcurrent detection circuit 15 that detects the current (overcurrent) of 13 and a reference value setting circuit 16 that sets a reference value of the power supply line 13 (motor current value), and an overcurrent detected by the overcurrent detection circuit 15. Based on the current value and the reference value set by the reference value setting circuit 16, for example, when the detected overcurrent value exceeds the reference value as described later, the power cutoff circuit 14 is operated to operate the power supply line 13. It is provided with a control circuit 17 or the like that mechanically shuts off.

Further, in the control circuit 17, a reset circuit 18 including a push button switch or the like capable of resetting the cutoff state of the power cutoff circuit 14 and an LED or the like provided on the insulating cover 11 for the cutoff state of the power cutoff circuit 14 are lit. A notification circuit 19 that can notify the operator by notifying or sounding a buzzer or the like (not shown) is connected.

The overcurrent detection circuit 15 includes, for example, a CT current sensor, a Hall element current sensor, an amplifier connected as needed, and the like, and constantly detects the current flowing through the power supply line 13 while the motor 3 is operating. Therefore, the detection signal (current value) is output to the control circuit 17. Further, in the reference value setting circuit 16, for example, the current value of about 1/2 to 1/4 of the average value of the overcurrent values generated at the time of kickback of the electric circular saw 1 obtained in advance by experiments or the like is not shown. It can be set by setting a variable resistor.

Further, the control circuit 17 has, for example, a microcomputer having a simple configuration, compares the detected overcurrent value with the reference value, outputs a cutoff signal to the power cutoff circuit 14, and sends a notification signal to the notification circuit 19. It is designed to output and notify the operator of the cutoff status. As the power supply for each circuit of the safety device 10, a DC power supply obtained by converting the AC power supply of the power supply line 13 with a converter (not shown) is used, but a battery (not shown) is built in the safety device 10 and this battery is used. Of course, it is also possible to use the power supply of.

Next, the operation of the safety device 10 will be described with reference to FIGS. 3 and 4. First, the plug 12 provided on the insulating cover 11 of the safety device 10 at the tip of the power cord 7 of the electric circular saw 1 is inserted into the AC commercial outlet 21 (see FIG. 5) at the work site. Then, while holding the handle 5 of the electric circular saw 1 and bringing the rotary blade 4 into contact with the cutting portion of the material to be cut, the power switch 6 of the handle 5 is turned on. When the power switch 6 is turned on, the motor 3 rotates at a preset predetermined rotation speed, the rotary blade 4 also rotates at the same time, and the material to be cut is cut at the cutting edge of the rotary blade 4.

During this cutting operation, if the rotary blade 4 is pinched by the material to be cut more than necessary, that is, if the rotary blade 4 is tightened by the material to be cut, a load is applied to the rotary blade 4 and an AC power supply (safety) is supplied to the motor 3. The current value of the power supply line 13) of the device 10 rises, and this rise in current (overcurrent) is detected by the overcurrent detection circuit 15 of the safety device 10 and input to the control circuit 17. The control circuit 17 compares the input overcurrent value with the preset reference value, and supplies a cutoff signal at the point K1 where the overcurrent value exceeds the reference value, for example, as shown in FIG. 3A. It outputs to the cutoff circuit 14 to operate the power cutoff circuit 14 to mechanically cut off the current supply line 13.

As a result, power is not supplied to the motor 3, the motor 3 is immediately stopped, and the rotation of the rotary blade 4 is also stopped at the same time. When the motor 3 and the rotary blade 4 are stopped, for example, the rotary blade 4 is tightened by the material to be cut during the cutting operation, and it becomes difficult for the rotary blade 4 to move smoothly along the cutting line, so that the operator can use the power switch 6 Even if kickback occurs when trying to pull out the electric circular saw 1 from the material to be cut in a hurry without turning off, the power supply line 13 to the motor 3 is forced and mechanically caused by the overcurrent due to the kickback. It will be cut off.

That is, according to the safety device 10, for example, the power supply line 13 can be forcibly and immediately cut off based on the overcurrent at the time of kickback, so that the operation of the electric circular saw 1 at the time of kickback The jumping up in the direction of the person is surely prevented, and the safety of the cutting work can be sufficiently ensured.

The detection of overcurrent is not limited to the method of detecting the rising point K1 of overcurrent as shown in FIG. 3A, and is not limited to the method of detecting the rising point K1 of overcurrent as shown in FIG. 3B, for example. The falling point K2 may be detected. That is, when the time t (time between the points K1 and K2) exceeding the reference value of the overcurrent is detected and this time t is longer (longer) than the preset reference time, the power cutoff circuit 14 is immediately shut off. To do.

Further, the reference value is not limited to one reference value, and for example, a plurality of (two or three or more) reference values may be set according to the type of the material to be cut, the type of the power tool, and the like. That is, for example, two reference values a and b are set as reference values, and when the overcurrent value exceeds at least one reference value of the two reference values a and b, the power cutoff circuit 14 is operated. By doing so, the detection accuracy of the overcurrent value is improved.

Then, in the case of the electric circular saw 1, when the power supply cutoff circuit 14 is cut off by the cutoff signal of the control circuit 17 due to the occurrence of the kickback or the like described above, the cutoff state is determined by the operator by the control circuit 17. It is designed to be maintained unless the operation of is performed. An example of the operation of the control circuit 17 during this operation will be described with reference to the flowchart of FIG.

As shown in FIG. 4, when power is supplied to the power supply line 13 and the electric circular saw 1 becomes usable, the program of the control circuit 17 starts (S01), and whether or not the power cutoff circuit 14 is activated is determined. Judgment (S02) is made. If "YES" in this determination S02, it is determined whether or not the reset circuit 8 is on, that is, whether or not the reset operation has been performed (S03), and if "YES" in this determination S03, that is, the power supply. When the cutoff circuit 14 is in operation and the reset circuit 18 is not turned on, the power cutoff circuit 14 is set to the connected state (S04), that is, the power cutoff circuit 14 is restored. If "NO" in the judgments S02 and S03, each judgment is repeated.

Then, if "YES" in the determination S04, that is, if the activated power supply cutoff circuit 14 is restored by the reset circuit 17, it is determined (S05) whether or not power is being supplied to the safety device 10. If "YES" in this determination S05, that is, if the activated power cutoff circuit 14 is restored and power is supplied to the safety device 10 from the plug 12 connected to the AC commercial outlet 21, the disconnection operation is continued. To do.

On the other hand, when a kickback or the like occurs and the operator suspends and does not continue the cutting work by the electric circular saw 1 in order to calm the mood (when the power cutoff circuit 14 is not restored or forgotten). ) Etc., the determination S06 becomes "NO", and for example, a series of programs ends (S07) after a predetermined time.

Since the operating state of the power cutoff circuit 14 can be confirmed by the operator by, for example, the LED lighting display of the notification circuit 19, when the disconnection operation is performed again after a predetermined time or the like, the LED lighting or the like is confirmed. This is possible by performing the reset operation by the reset circuit 18 described above. That is, once the power cutoff circuit 14 is cut off due to an overcurrent, the power cutoff circuit 14 does not return to the connected state unless the reset circuit 17 is turned on, and it is impossible to continuously perform the disconnection operation. Become.

As described above, according to the electric round saw 1, the safety device 10 sets the overcurrent value and the reference value detected by the overcurrent detection circuit 15, the reference value setting circuit 16, the power supply cutoff circuit 14, and the overcurrent detection circuit 15. Since it has a control circuit 17 that operates the power supply cutoff circuit 14 based on the reference value set in the circuit 16 to cut off the current supplied to the motor 3, the power cutoff circuit reliably detects the overcurrent due to kickback or the like. 14 can be shut off to immediately stop the motor 3 and the rotary blade 4, and sufficient safety during cutting work can be ensured.

In particular, since the motor 3 is an AC100V motor, the motor 3 is connected to the AC100V power supply as the motor power supply via the power cord 7, and the safety device 10 is arranged in the AC plug of the power cord 7, the AC It is possible to reliably take measures against kickback of the power-type electric circular saw 1 and easily obtain the electric circular saw 1 with sufficient safety.

Further, since the safety device 10 is integrated with the plug 12, the safety device 10 can be used by simply inserting the plug 12 into an AC commercial outlet 21 as an AC power source, and an electric circular saw with a safety device having excellent usability. The saw 1 can be easily obtained. Further, once the power cutoff circuit 14 is cut off due to an overcurrent, the power cutoff circuit 14 does not return to the connected state unless the reset circuit 17 is turned on. Therefore, the power cutoff circuit 14 is continuously cut off in the cutoff state. It is possible to further improve the safety of the cutting work, for example, the safety can be confirmed automatically after the cutoff state.

FIG. 5 shows an example of a power tool safety device according to the present invention. Hereinafter, the same parts as those in the above embodiment will be described with the same reference numerals. In the case of the safety device 10, the safety device 10 is integrally provided with the plug at the tip of the power cord 7 of the electric circular saw 1, whereas the plug at the tip of the power cord 7 of the electric circular saw 1 is provided. It can be retrofitted between the AC commercial outlets 21.

That is, an outlet 22 into which the plug of the power cord 7 of the electric circular saw 1 can be inserted is arranged on the front surface of the insulating cover 11, and the plug 23 is arranged on the rear surface of the insulating cover 11. Then, the pair of terminals 22a of the outlet 22 and the pair of terminals 23a of the plug 23 are connected by a predetermined cable in the insulating cover 11 to form the power supply line 13, and each of the above is formed inside the insulating cover 11. Circuits 14 to 19 and the like are built-in.

Then, the plug of the electric circular saw 1 is inserted and connected to the outlet 22, and the plug 23 is inserted and connected to the AC commercial outlet 21, that is, the outlet 22 and the plug 23 are integrated into the safety device 10, so that the electric circular saw 1 is connected. The safety device 10 can be connected between the power cord 7 and the commercial outlet 21.

Also in this embodiment, in addition to obtaining the same action and effect as the electric circular saw 1, since the safety device 10 can be retrofitted, it can be easily attached to the existing electric circular saw 1 and safety by kickback or the like. It is possible to secure and easily secure the electric circular saw, and it is not necessary to purchase an electric circular saw 1 with a new safety device, and it is possible to reduce the financial burden on the user of the electric circular saw 1. Be done.

In the above embodiment, the case where the power tool is an AC power supply type electric circular saw 1 has been described, but the present invention is not limited to this, and the power tool also includes an electric saw having a saw as a tool that moves back and forth. It goes without saying that it can be applied and can be used for various power tools other than saws that use an AC power supply with an appropriate voltage. Further, the embodiment of the electric circular saw 1, the embodiment of the rotary blade 4 to be used, the circuit configuration of the safety device 10, and the like in the above embodiment are also examples, and are appropriate as long as they do not deviate from the gist of each invention of the present invention. The configuration can be adopted.

The present invention can be used not only for electric tools using an AC power supply but also for all electric tools connected to electric parts such as motors using a power cord.

1 ... Electric round saw, 2 ... Housing, 3 ... Motor, 4 ... Rotary blade, 5 ... Handle, 6 ... Power switch, 7 ... Power cord, 10 ...・ Safety device, 11 ・ ・ ・ Insulation cover, 12 ・ ・ ・ Plug, 13 ・ ・ ・ Power supply line, 14 ・ ・ ・ Power cutoff circuit, 15 ・ ・ ・ Overcurrent detection circuit, 16 ・ ・ ・ Reference value setting circuit , 17 ... control circuit, 18 ... reset circuit, 19 ... notification circuit, 21 ... AC commercial outlet, 22 ... outlet, 23 ... plug.

Claims (6)

A motor disposed in a housing and a tool is mounted on the rotating shaft, a power switch connected to the motor, and a power switch connected to the motor power supply such as an outlet, and the motor is connected outside the housing. An electric tool with a safety device, which comprises a safety device capable of cutting off the power supply from the motor power supply to the motor when an overcurrent is detected. The safety device includes an overcurrent detecting means for detecting an overcurrent by the motor, a reference value setting means capable of setting a predetermined reference value, a power cutoff means connected to the power supply line of the motor, and the overcurrent. It is characterized by having a control means for operating the power cutoff means to shut off the power supplied to the motor based on the overcurrent value detected by the current detecting means and the reference value set by the reference value setting means. The electric motor with a safety device according to claim 1. A claim characterized in that the motor is an AC motor, the motor is connected to an AC power source as the motor power source via a power cord, and the safety device is arranged in an AC plug of the power cord. Item 2. The electric motor with a safety device according to item 1 or 2. The power tool with a safety device according to claim 3, wherein the safety device is integrated with the AC plug. An outlet provided on one surface of the insulating cover to which a plug of an electric tool can be connected, a plug provided on the other surface of the insulating cover and connectable to an outlet for a motor power supply, and an outlet provided in the insulating cover. An overcurrent detecting means for detecting an overcurrent of a power supply line formed between the power supply line and a plug, a reference value setting means capable of setting a predetermined reference value, a power cutoff means connected to the power supply line, and the overcurrent. It is characterized by including a control means for operating the power cutoff means to shut off the power supplied to the motor based on the overcurrent value detected by the detection means and the reference value set by the reference value setting means. Safety device for electric tools. The power tool according to claim 5, wherein a notification means capable of notifying the cutoff state of the power cutoff means and a reset means for resetting the cutoff state of the cutoff means are provided in the insulating cover. Safety device for.

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