JPH0223237Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an electric cutting tool such as an electric nipper or electric scissors.

(Prior Art) In this type of conventional electric cutting tool, a manual switch is generally used to control the rotational direction of the drive motor.

(Problem that the invention aims to solve) However, with conventional electric cutting tools, when the cutting material exceeds the cutting capacity of the electric cutting tool, the electric cutting tool cannot cut the cutting material completely, and the gap between the pair of cutting blades The rotation of the drive motor was stopped with the cutting material sandwiched between them, and the polarity of the voltage applied to the motor was changed using a manual switch to open the cutting blade. Therefore, when cutting is impossible, the windings of the drive motor are burnt out due to overcurrent caused by overload, and the gears are damaged due to overload.

That is, with conventional electric cutting tools, when it is impossible to cut the material to be cut, after the drive motor has stopped rotating, the polarity of the voltage applied to the motor is switched by manually operating the motor's rotation direction switch. The only option was to reverse the direction of rotation and release the pair of cutting blades of the electric cutting tool.

On the other hand, with electric cutting tools, various loads are applied to the cutting blade depending on the material to be cut, so that the cutting capacity may be exceeded and cutting may not be possible.

Therefore, in cutting tools in which the rotational direction of the drive motor is changed by operating a manual switch, overload can conventionally be detected only by visual inspection by the operator, which can cause burnout of the motor windings due to overcurrent associated with overload, as well as overload. It was not possible to prevent damage to the gear due to

In view of the above-mentioned problems, the present invention is designed to reliably prevent burnout of motor windings and damage to motor gears and the like due to overcurrent.

(Means for solving the problem) The technical means of the present invention for solving this technical problem is to drive the pair of cutting blades 1 by normal rotation of the motor 2.
In an electric cutting tool in which at least one of the cutting blades 10 and 11 is opened and closed relative to the other cutting blade 11, an open stop position detection switch 24 detects the open stop position of the cutting blades 10 and 11. An overcurrent detection circuit 39 is provided to detect overcurrent to the motor 2, and the cutting blades 10 and 11 are opened until the open position detection switch 24 is in the detection state upon detection by the overcurrent detection circuit 39. The point is that a cutting blade release circuit 40 for driving the motor 2 in reverse is provided.

(Function) During normal operation, the movable contact c of the switch 24 is connected to the contact b, so when the operating switch 23 is closed, voltage is applied to the thyristor 29, the thyristor 29 is triggered, and the relay 28 is activated. The motor 2 rotates normally, and the cutting tool 9 cuts the material to be cut. At this time, the voltage drop across the resistor 36 is small, and the motor 2 continues to rotate normally without triggering the gate of the thyristor 32, repeatedly cutting the cutting material. However, when attempting to cut a material that exceeds the cutting capacity of the cutting tool 9, the rotation of the motor 2 stops with the cutting tool 9 sandwiching the cutting material, and an overcurrent flows to the motor 2 due to the overload. The voltage drop across the resistor 36 becomes large and triggers the gate of the thyristor 32, which turns off the thyristor 29, returns the relay 28, and reverses the polarity of the voltage applied to the motor 2, reversing the direction of rotation of the motor 2. Then, the cutting blade 1 of the cutting tool 9
0 and 11 are opened. When the switch is reversed to the open stop position, the connection of the movable contact c of the open stop position detection switch 24 is switched from contact a to contact b, triggering the gate of the thyristor 29, the thyristor 29 is turned off, and at the same time, the capacitor 30 A reverse voltage is applied to the thyristor 32 due to the charge stored in the thyristor 32, the thyristor 32 is turned off, the relay 28 is activated, the polarity of the voltage applied to the motor 2 is reversed, and the motor 2 rotates normally again. The cutting tool 9 repeats the cutting operation. At this time,
If the operating switch 23 is in the open state, the movable contact c of the switch 24 is connected to the contact a at the open stop position.
The contact is switched from contact b to cut off the voltage supplied to the motor 2, and the rotation of the motor 2 is stopped.

(Embodiment) Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. In FIG. 2, 1 is a cutting tool main body, 2 is a geared motor housed in the main body 1,
The output shaft 4 is configured to be driven in the forward and reverse directions around the axis via the shaft. Reference numeral 5 denotes a cam having a cam surface 6, which is externally fitted and fixed to the output shaft 4, and the cam surface 6 of the cam 5
A crank 7 is provided protrudingly on the opposite side.

Reference numeral 9 denotes a cutting tool such as scissors or nippers, which has a pair of cutting blades 10 and 11, and each cutting blade 1.
The cutting blades 10, 11 and the operating parts 12, 13 are opened and closed, respectively, between the cutting blades 10, 11 and the operating parts 12, 13. Bracket 1 of main body 1
4 so as to be rotatable around a pivot shaft 15. Between the operation parts 12 and 13, the operation parts 12 and 1
A pressing spring 16 is provided to widen the interval between the two. One operating section 13 is fixed to the main body 1 side, and as shown in FIG. When the output shaft 4 rotates in the normal direction, the crank 7 first presses the operating part 12 against the spring 16 to close the cutting blades 10 and 11, and then, by half a revolution of the output shaft 4, the crank 7 presses the operating part 12 against the spring 16. The space between the operating parts 12 and 13 is increased by loosening the pressure on the operating parts 12 and 13. Therefore, one cutting blade 10 opens and closes relative to the other cutting blade 11 for each rotation of the output shaft 4.

FIG. 1 shows an electric circuit diagram of a motor drive device for driving the motor 2 in forward and reverse directions.
21 is a + terminal, 22 is a - terminal, and these terminals 2
A DC voltage is supplied between 1 and 22. 23
is an operating switch for operating the cutting tool 9;
As shown in FIG. 2, the main body 1 is provided in an outwardly projecting manner, and is configured to be closed by pressing the outwardly projecting operating portion 23a. Reference numeral 24 denotes an open position detection switch for detecting the open stop position of the cutting blades 10, 11, which is constituted by a microphone switch, and is incorporated into the main body 1 and placed near the cam 5, as shown in FIG. When the distance between the cutting blades 10 and 11 is within a predetermined width, the open position detection switch 24 has its actuating piece 24a pressed by the cam 5 and the movable contact c connects to the contact a side. When the distance between the movable contacts c and b increases by a predetermined width or more, the pressure of the cam 5 on the operating piece 24a is released and the movable contact c is connected to the contact b side. 25 and 26 are resistors, 27 is a diode, 2
8 is a relay, 29 is a thyristor, and when the operating switch 23 is closed, the DC voltage is applied to the thyristor 2.
9, and at this time, the movable contact c of the switch 24 is connected to the contact b, so the thyristor 2
9 is triggered, the relay 28 is activated, which causes the motor 2 to rotate forward, and the crank 7 to rotate the output shaft 4.
Rotating around, the cutting tool 9 cuts the material to be cut. Then, when the operating switch 23 is closed and the movable contact c of the switch 24 is switched from the contact b to the contact a by the rotation of the cam 5, the operating switch 23 is closed.
Even when the motor 2 is opened, the motor 2 continues to drive until the cutting blades 10 and 11 reach the open stop position, and then stops.

30 is a capacitor, 31 is a resistor, 32 is a thyristor, 33 and 34 are resistors, 35 is a capacitor, 3
6 is a resistor, 37 is a diode, and when the cutting tool 9 attempts to cut a material that exceeds its cutting capacity and the cutting blades 10 and 11 sandwich the cutting material and the rotation of the motor 2 stops, the power is applied to the motor 2. As the supply current increases and the voltage drop across the resistor 16 increases, the gate voltage of the thyristor 32 increases, and the voltage divided by the resistor 34 and the resistor 33 triggers the gate of the thyristor 32. It is configured. Also, at this time, due to the electric charge of the capacitor 30 that was being charged via the resistor 31,
A reverse voltage is applied to the thyristor 29, the thyristor 29 is turned off, the relay 28 is reset, the polarity of the voltage applied to the motor 2 is switched, and the motor 2 is turned off.
is configured to drive in reverse. and,
The cam 5 linked to the rotation of the crank 7 is the cutting blade 1
When the switch is reversed to the open stop position of 0, 11, the movable contact c of the switch 24 is connected to the contact b again,
The thyristor 29 is triggered, the relay 28 is activated, the motor 2 rotates forward, and the cutting tool 9 performs a cutting operation.

An overcurrent detection circuit 39 for detecting overcurrent to the motor 2 is composed of resistors 33, 34, 36, a capacitor 35, a diode 37, and the like. A cutting blade opening circuit 40, which drives the motor 2 in reverse until the opening position detection switch 24 enters the detection state upon detection by the overcurrent detection circuit 39, is composed of a relay 28, a capacitor 30, a resistor 31, a thyristor 32, and the like. There is. In addition, the diode 37, the resistor 34, and the capacitor 35 are connected to each other by a voltage drop across the resistor 36 when the current supplied to the motor 2 increases due to an instantaneous overload such as when the motor 2 is started or when cutting material. A time constant circuit is configured to prevent the thyristor 32 from triggering. The motor drive device shown in FIG. 1 is incorporated into the cutting tool main body 1 shown in FIG. 2.

In the above embodiment, the motor 2 is used to open and close one cutting blade 10 relative to the other cutting blade 11, but instead of this, the motor 2 is used to open and close both cutting blades 10 and 11 relative to each other. It may be moved. Further, in the above embodiment, the output shaft 4 is rotated in the direction of the arrow a by the forward rotation of the motor 2 to open and close the cutting blades 10 and 11, but instead of this, the forward rotation of the motor 2 is The output shaft 4 is set to rotate in the direction opposite to the direction of the arrow a, and under normal conditions, the output shaft 4 is rotated in the direction opposite to the direction of the arrow a to open and close the cutting blades 10 and 11. The output shaft 4 may be set to rotate in the direction of arrow a.

(Effects of the invention) According to the invention, even when an overload is applied to the electric cutting tool, the cutting blades 10 and 11 can be automatically opened and closed reliably. It is possible to effectively prevent burnout, prevent damage to the gears of the motor 2 due to overload, and reduce damage to the cutting blades 10 and 11, and the practical effects thereof are significant.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is an electric circuit diagram, Fig. 2 is a perspective view, and Fig. 3 is a diagram showing A-A in Fig. 2.
It is an A-line sectional view. 2... Geared motor, 10... Cutting blade, 11
... Cutting blade, 24 ... Open position detection switch, 3
9... Overcurrent detection circuit, 40... Cutting blade release circuit.

Claims (1)

[Claims for Utility Model Registration] By the normal rotation drive of the motor 2, the pair of cutting blades 1
In an electric cutting tool in which at least one of the cutting blades 10 and 11 is opened and closed relative to the other cutting blade 11, an open stop position detection switch 24 detects the open stop position of the cutting blades 10 and 11. and an overcurrent detection circuit 39 for detecting overcurrent to the motor 2,
Due to the detection by the overcurrent detection circuit 39, the cutting blade 10,
An electric cutting tool characterized in that a cutting blade opening circuit 40 is provided for driving the motor 2 in reverse so as to open the cutting blade 11.