JPH07275288A - Liquid crystal filter shading control device for welding mask without operating power switch - Google Patents

Abstract

PURPOSE:To enable the dark change and shading of a liquid crystal filter without an operating power switch so as to improve the workability of a welding worker, and impede the generation of wrong dark change by sunlight, by using a photodiode as an optical sensor, and using a low frequency eliminating filter circuit. CONSTITUTION:The photocurrent of a photodiode PD by sunlight and pulse incident light is voltage-amplified by an amplifier 2a, and after eliminating the sunlight of low frequency by a filter circuit 3, the photocurrent is amplified by an a.c. amplifying part 4 and an adding amplifying part 6. The first trigger pulse from an output end T1 is then inputted to a first monostable multivibrator 7, and in the on-state of the first monostable multivibrator 7, the second trigger pulse from first reverse output Q2 is inputted to the second input trigger terminal B of a second monostable multivibrator 8. A power circuit part 9 put in the on-state by the output of the second output Q3 puts a liquid crystal filter in the dark change and shading state by the output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided with a welding mask used during welding work so as to detect intense light when an arc occurs and automatically apply a voltage to a liquid crystal filter. , With this, the light blocking degree of the filter can be changed to reliably protect the eyes of the worker, and if the occurrence of the arc is stopped, the transparency of the liquid crystal filter can be automatically returned to the original state. The present invention relates to a liquid crystal filter light-shielding control device for a welding mask that does not hinder work while wearing the welding mask.

[0002]

2. Description of the Related Art In conventional welding masks, a mere light-shielding glass was used as a filter. Therefore, during normal work, the mask is often removed and the mask is put on immediately after the arc is generated. Not only will it hurt, but the workability will also be extremely poor. Therefore, in order to eliminate the above-mentioned defects, the sensor receives the intense light by utilizing the characteristics of liquid crystal, and the output signal of the sensor is introduced into an electric control circuit to automatically turn on / off the liquid crystal filter. Masks have already been developed which are controlled so that the light transmittance of the filter can be reduced, eyes can be protected and workability can be improved.

As the above-mentioned conventional example, for example, a circuit configuration as shown in FIG. 5 is known. In this case, first and second phototransistors P which are light sensors are known.
Tr ₁ and PTr ₂ are provided behind the optical filter a, and the first phototransistor PTr ₁ forms the first tapered entrance b ₁ capable of receiving the light L ₁ having a narrow viewing angle so that the arc light is mainly detected. The second phototransistor PT
With respect to r _2, the viewing angle of the second taper entrance b _{2 is} made sufficiently larger than that of the former, and a light shield c is provided on the optical axis to prevent the arc light from directly entering. , For the normal ambient light, the former PTr
_The viewing angle is made large so that the light L ₂ that exceeds the received light amount of ₁ can be received.

Here, the first and second phototransistors PT
r ₁ and PTr ₂ are DC power source E and operation power switch SW
Form a series closed circuit d, and the optical filter a has a practical tunnel current flowing through the series closed circuit d even when sunlight or the like is incident on it in the daytime outdoors from various directions. It has a concentration that can be restricted so that it falls within the range.

Further, as shown in FIG. 1, first and second phototransistors PTr ₁ and PTr are connected in series in the forward direction.
A resistor g is connected between the connection point e of Tr ₂ and the positive power supply line f to which a positive voltage is applied by the closing operation of the operation switch SW, and between the terminals of the resistor g. A multivibrator circuit M including resistors h ₁ and h ₂ , a capacitor i, and exclusive OR circuits j ₁ , j ₂ and j ₃ as ICs is connected to the.

Therefore, by the exclusive OR circuit j ₃ ,
The connection point e functions as an inverter and a buffer depending on whether it is logic 1 or 0, and a liquid crystal filter (not shown) is connected to the output terminals k ₁ and k ₂ of the multivibrator circuit M.

In the above conventional example, when there is no arc light due to welding, the second phototransistor PTr _{2 has} a larger amount of received light than the first phototransistor PTr ₁ , and therefore the potential at the connection point e is It is on the plus side of the DC power supply E, so the logic at the connection point e becomes 1 and
The exclusive OR circuit j ₃ serves as an inverter and the output terminal k
_{Since 1} and k ₂ have opposite phases and an alternating rectangular wave voltage is applied to the liquid crystal filter, the transparency of the liquid crystal filter is high and the surroundings appear bright.

Then, when the welding light is generated, the amount of light received by the first phototransistor PTr ₁ becomes the second
The phototransistor PTr ₂ is drastically increased from that of the phototransistor PTr ₂ , and as a result, the potential of the connection point e becomes the negative side of the DC power supply E, and the logic of the same point e becomes zero. As a result, the exclusive OR circuit j ₃ becomes a buffer, so that the output terminal k
_{Since 1} and k ₂ have the same phase, the voltage applied to the liquid crystal filter disappears, the transmittance of the liquid crystal filter is reduced, and the dark state is brought about. Therefore, the arc light can be dealt with.

[0009]

According to the above-mentioned conventional example, no matter how bright the surroundings are,
In addition, even when it is dark, the light blocking degree of the liquid crystal filter can be controlled over a wide range without any adjustment, which is superior to the previous light blocking control device. Therefore, two phototransistors are used. In addition, as described above, a complicated structure in which the first and second tapered entrances b ₁ and b ₂ and the light shield c are provided is required.

More importantly, it is necessary to activate the DC power source E by operating the operation power switch SW. Therefore, as shown in FIG. Therefore, as shown in the front view (B) of FIG.
Is set from the inside as shown in FIG. 9A and is fixed by the set screw p. However, the liquid crystal filter light-shielding control device q is built in the filter frame o, and the operation switch SW
6A is exposed from the filter frame body o to the operator's face side as shown in FIG. 6A. In the figure, r ₁ is the front transparent plate, r ₂ is the back transparent plate, and S is In the liquid crystal filter, the first and second phototransistors PTr ₁ and PTr ₂ are provided on the upper side of the filter frame body o toward the front side.

Therefore, when the conventional welding mask M is used, since the operation power switch SW is provided in front of the welding operator, the DC power source E is turned on after the welding mask is put on. Even if an ON-OFF operation is attempted, the operation must be performed by inserting a finger from between the mask body m and the face while wearing the wear mask, resulting in extremely poor operability. Must be removed and operated.

Further, since the operation power switch SW must be operated with a fingertip, the filter frame body o is covered by the attachment of a dustproof protective plate or the like, which prevents dust from entering the inside. If you try, you have a flaw that makes it impossible.

In view of the above-mentioned drawbacks of the conventional example, the present invention uses a plurality of phototransistors and eliminates the need to manually turn on or off the operation power switch during use. To do. Therefore, in the present invention, a photodiode is used as a light sensor, and a photocurrent is generated in itself by the incidence of light on the sensor, and the photocurrent is utilized. In addition, manual ON-OFF control of the DC power source for the light sensor is unnecessary, and the above photocurrent is input to the subsequent monostable multivibrator. By applying power,
Also in this case, the ON / OFF operation of the DC power supply is unnecessary.

Further, in the present invention, by connecting a filter circuit for removing low frequency components of the photocurrent by the above-mentioned photodiode, the output of the photocurrent due to natural light such as sunlight is not amplified and the welding light is not amplified. By amplifying only the pulsed photocurrent due to, for example, darkening of the liquid crystal filter due to natural light can be prevented, and the output from the monostable multivibrator described above is input to the power supply circuit section provided in the preceding stage of the liquid crystal filter. By doing so, the power supply circuit unit is brought into an operating state, and thereby, it is intended to provide a liquid crystal filter light-shielding control device having a simple configuration and having no operation power supply switch and having high reliability.

[0015]

In order to achieve the above-mentioned object, the present invention includes a summing amplification section and a first amplification section from a DC power supply circuit.
A DC voltage is applied to the monostable multivibrator and the second monostable multivibrator, a photodiode that generates a photocurrent by pulsed incident light including ambient light, and an amplifier that amplifies the photocurrent by voltage are provided. A detection amplifying unit having, a filter circuit for removing low frequency components from the output of the detection amplifying unit, an AC amplifying unit for amplifying an AC output from the filter circuit, and a predetermined voltage for the amplified AC output. A summing amplifier for adding and amplifying, and a first trigger input terminal of the first monostable multivibrator to which the first trigger pulse from the summing amplifier is input to be in an ON state, A second trigger pulse is applied to the second trigger input terminal of the second monostable multivibrator from the first inverted output of the first monostable multivibrator, From the second output of the second monostable multivibrator, the power supply output is applied to the power supply circuit section connected to the liquid crystal filter, and the output from the power supply circuit section is applied to the liquid crystal filter. , Second
The dark state of the liquid crystal filter is maintained for a predetermined period of time determined by a timer capacitor and a resistor that are external to the monostable multivibrator, and the addition voltage to the summing amplifier is set to the second monostable multivibrator. It is intended to provide a liquid crystal filter light-shielding control device for a welding mask, which does not have an operation power switch, which is characterized in that it is introduced from the second inverted output.

[0016]

With the liquid crystal filter light-shielding control device for a welding mask according to the present invention, not only natural light (disturbance light) but also pulsed light that instantaneously changes like welding light is generated.
As a result, a photocurrent is generated that is proportional to the intensity of the incident light, which is voltage-amplified in the detection / amplification unit and passed through the filter circuit in the next stage, and then input to the AC amplification unit in the next stage. Is input to the addition amplification section.

As a result, low frequency components such as sunlight are removed by the filter circuit, and the signal due to the gradual change in the light amount input from the detection amplification section to the AC amplification section becomes weak. The signal is amplified and input to the addition amplification unit.

In the adding amplifier, the voltage from the second monostable multivibrator is added to the amplified AC output to amplify the voltage. Therefore, the first monostable is generated by the first trigger pulse from the adding amplifier. Since the multivibrator is in the ON state and the second trigger pulse is applied to the second monostable multivibrator, the output of the second monostable multivibrator is for the external timer. For a predetermined time determined by R and C,
It is applied to the next-stage power supply circuit section.

As a result, the power supply circuit section is brought into an operating state, and its output is applied to the liquid crystal filter, so that the dark state is maintained for a predetermined time determined by the time constant, and the welding operator's eyes are kept. Protect.

Of course, if only natural light is generated and no pulsed light is generated, the output of the summing amplification section is in the LOW state, as is clear from the above-mentioned instruction, so the output of the first monostable multivibrator becomes LOW, No output is applied from the second monostable multivibrator to bring the power supply circuit section into an operating state, and no power is supplied to the liquid crystal filter, so that the translucent state is maintained.

Further, it is not necessary to supply electric power from the DC power supply circuit to the photodiode, which is an optical sensor, and a DC power supply circuit is connected to the summing amplification section and the first and second monostable multivibrators. Therefore, it is possible to exert the light-shielding action by the liquid crystal filter as described above without the operation power switch for supplying the power.

[0022]

The present invention will be described in detail with reference to the embodiments shown in the drawings.
As shown in FIG. 2, the welding mask M is the same as the conventional example.
A mask window m is opened in the mask body m, and a filter frame body o is fitted into the cut window n from the inside (back side of the paper surface). In the figure, r ₁ is a front transparent plate, S is a liquid crystal filter, and a photodiode PD, which will be described later, is on the upper side of the filter frame o and is on the back side of the front transparent plate r ₁ . Exposed to.

An embodiment of the liquid crystal filter light-shielding control device D will be described in detail below with reference to FIG. 1. The DC power supply circuit 1, the detection amplification section 2, the filter circuit 3, the AC amplification section 4, the filter circuit 5 will be described. , A first monostable multivibrator 7, a second monostable multivibrator 8, a power supply circuit section 9, and a liquid crystal filter circuit section 10 having a liquid crystal filter S.

An example of the above DC power supply circuit 1 is
It is composed of a battery 1a and a voltage stabilizer 1b, and its power supply terminal 1c is connected to the summing amplifier 6 and the first and second monostable multivibrators 7 and 8 to apply the DC voltage. .

Next, the detection / amplification unit 2 has the photodiode PD, the amplifier 2a, the capacitor C ₁ and the resistor R _{1 described above.}
In this case, when pulsed light such as welding light is incident together with natural light, a photocurrent proportional to the intensity of the incident light flows, which is voltage-amplified by the amplifier 2a. Introduced in 3.

What is shown as the filter circuit 3 is a CR filter composed of a capacitor C ₂ and a resistor R ₂ , so that a pulse element such as ambient light such as sunlight is included in the photocurrent. Since a low frequency component having a small amount is cut, a pulse component is introduced into the AC amplification unit 4 in the next stage, and the AC amplification unit 4 is connected to the AC amplifier 4
a and resistors R ₃ , R ₄ and R ₅ .

In the illustrated embodiment, the output of the AC amplifying section 4 is not directly inputted to the adding amplifying section 6, but the output of the AC amplifying section 4 is also provided between the capacitor C ₃ and the resistor R ₆ by RC.
Although the filter circuit 5 as a filter is interposed, this is not an essential element and can be omitted. At this time, in the illustrated example, the low frequency component is removed again to prevent the operational amplifier 6a in the addition amplification unit 6 from oscillating.

Further, the summing amplification section 6 comprises an operational amplifier 6a, a capacitor C ₄ , resistors R ₇ , R ₈ , R ₉ and a resistor R _10, and a variable resistor VR, which will be described later in detail. When the output of the second inverted output Q ₄ of the monostable multivibrator 8 is “H”, the resistance R ₁₁ and the variable resistance V
The voltage divided by the resistance value of R is configured to be input to the operational amplifier 6a in the addition amplification unit 6 via the resistor R ₁₀ .

Therefore, in the summing amplification section 6 described above,
In order that the circuit of the first monostable multivibrator 7, which is the next stage, can be turned on by the output signal from the AC amplification unit 4 introduced through the filter circuit 5, the above-mentioned divided voltage is applied. , Is added to the above output signal and amplified.

Next, the output terminal T ₁ of the summing amplifier 6 is connected to the first trigger input terminal A of the first monostable multivibrator 7, the external capacitor C ₅ and the external resistor R are connected.
₁₂ and a capacitor C _6, and the output pulse width (output time) of the first monostable multivibrator 7 is determined by the C ₅ and R _12, and the first output Q ₁ thereof is The resistor R ₁₃ and the variable resistor VR are connected to the resistors R ₆ and R ₂ and the photodiode PD on the positive side, which is grounded, and between the variable resistor VR and the resistor R ₁₃ . The inverted output Q _{4 of} the second monostable multivibrator 8 is inputted via the through resistor R ₁₁ .

The first inverted output Q ₂ of the first monostable multivibrator 7 is the second monostable multivibrator 8
In the second monostable multivibrator 8, which is connected to be input to the second trigger input terminal B of
C ₇ , R ₁₄ and R ₁₅ are external capacitors and external resistors like C ₅ and R _12, and the time constant of the timer is determined by this, and its second output Q ₃ is in the “H” state. As a result, the output of the second monostable multivibrator 8 is input to the power supply circuit section 9 of the next stage through the resistor R ₁₆ for a predetermined period of time according to the above time constant.

The power supply circuit section 9 illustrated above is a known one per se, and includes a diode d, a switch 9a for varying the light blocking degree of the liquid crystal filter S, and exclusive OR circuits IC ₁ and IC. ₂ , IC ₃ , IC ₄ , resistance R
₁₇ and R ₁₈ and capacitors C ₈ and C ₉ are provided,
The liquid crystal filter circuit unit ₁₀ is configured by connecting a pair of liquid crystal filters S to the output side of the power supply circuit unit 9, and one of the liquid crystal filters is darkened by switching the changeover switch SW. It is already known that both liquid crystal filters can be put in a dark state.

Here, as the liquid crystal filter S, a known one will be used. For the reason, as shown in FIGS. 3 and 4, the light source side liquid crystal filter S ₁ and the eye side liquid crystal will be described. The lead-out terminals t _a and t _b and the common terminal t ₀ are formed by stacking with the filter S ₂ . Furthermore, the general-purpose liquid crystal filter S is in the closed gap formed by the separator S ₅ which is sandwiched between 4 to two as explicitly glass plate S _3, S _4, a nematic liquid crystal S ₆
And the lead-out terminals S ₇ and S ₈ of the transparent electrodes laid on both sides of each glass plate S ₃ and S ₄ are made to go out.

[0034] The glass plate S _3, the surface of S ₄ is obtained by coating treatment by polarizing film S _9, S _10, by determining the polarization axis of the polarizing film S _9, S ₁₀ appropriately, a nematic liquid crystal S ₆ is an OFF state in which light is cut off in the ON state where a voltage is applied to the extraction terminals S ₇ and S ₈ and a voltage is not applied
Can be made transparent in the state of
It is also possible to reverse the relationship between FF and transparency.

When the liquid crystal filter light-shielding control device D having the configuration as shown in FIG. 1 is used, only ambient light such as natural light is incident on the photodiode PD of the detection / amplification unit 2, and pulse light is incident from the AC light source. If not, the output from the output terminal T ₁ of the operational amplifier 6a in the summing amplification unit 6 is in the “L” state due to the presence of the filter circuits 3 and 5.
Therefore, the first inverted output Q ₂ of the first monostable multivibrator 7 remains “H”. From this, the second output Q ₃ in the second monostable multivibrator 8 is “L”, and as a result, since there is no input to the power supply circuit unit 9, there is no power supply to the liquid crystal filter circuit unit 10, The liquid crystal filter S holds the translucent state.

Next, if the welding light is incident or the front surface of the photodiode PD is momentarily shielded by the palm of the hand so that the pulse light is incident, it is proportional to the intensity of the pulse incident light. An output current, which is a photocurrent, is generated,
After being voltage-amplified by the amplifier 2a of the detection amplification unit 2,
The low-frequency component due to the ambient light in the photocurrent is removed by the filter circuit 3 in the next stage, and the AC amplifier 4 in the next stage is further removed.
Amplifies the AC signal by.

The amplified alternating-current signal has low-frequency components cut off by the filter circuit 5 in the next stage.
Since the second monostable multivibrator 8 is in the OFF state, the second inverted output Q ₄ of the second monostable multivibrator 8 is “H”.
_The voltage divided by ₁₁ and the variable resistance VR is the resistance R ₁₀
Via the filter 5, and as a result, the voltage is added to the signal input to the addition amplification unit 6 via the filter 5 to be amplified, and the output terminal T ₁ thereof becomes “H”, and the first
A first trigger pulse sufficient to turn on the monostable multivibrator 7 is applied to the first trigger input terminal A.

Therefore, a rising pulse is input to the first trigger input terminal A, the first monostable multivibrator is turned on, and as a result, the first output Q ₁
Becomes "L", and the falling pulse having one pulse having a constant width is applied as the second trigger pulse to the second trigger input terminal B of the second monostable multivibrator 8 in the next stage, whereby The second output Q ₃ becomes “H”, and the power supply circuit unit 9 is turned on. The elapsed time of the ON state is determined by the timer capacitor C ₇ and the resistors R ₁₄ and R ₁₅ . .

Thus, as is known, the exclusive OR circuit I
C _1, the IC _2, IC _3, IC ₄ the power supply circuit unit 9 having, when the switch 9a is turned ON, the next stage of the liquid crystal filter S is shown a sufficient light blocking and all darkened, OFF In that case, only one of the liquid crystal filters will be in a dark state, and light can be shielded from the dark state to the light state.

[0040]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, only a photodiode is required as an optical sensor, and not only a relatively simple structure can be obtained but also an optical sensor circuit and the like can be obtained. It is possible to eliminate the need for an operation power switch for applying the power, and therefore, it is possible to eliminate the inconvenience of the welding operator manually inserting the operation switch by inserting his / her finger into the welding mask.

Further, the DC power supply circuit is connected in advance to necessary components and is provided with an electric filter for removing low frequency components at appropriate places. There is no inconvenience that the input is applied to the power supply circuit section by the incident light and the liquid crystal filter is in a dark state, and if pulsed light such as welding light is incident, there is no need to manually operate the operation power switch.
The liquid crystal filter can be darkened, a welding mask which is extremely easy to use can be provided, and since the operation power switch is not required, the filter frame can be covered with the dustproof protection plate.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an embodiment showing a liquid crystal filter light shielding control device for a welding mask according to the present invention.

FIG. 2 is a front view showing a main part of a welding mask provided with the above liquid crystal filter light-shielding control device.

FIG. 3 is a schematic side view of a laminated liquid crystal filter used in the same device.

4A is a perspective view of a liquid crystal filter, and FIG. 4B is a vertical front partial view of FIG. 4A.

FIG. 5 is an electric circuit diagram showing a conventional liquid crystal filter light shielding control device.

6A is a transverse rear view showing the inner surface side of a conventional welding mask, and FIG. 6B is a front view showing the main part of FIG. 6A.

[Explanation of symbols]

1 DC power supply circuit 2 Detection amplification part 2a Amplifier 3 Filter circuit 4 AC amplification part 6 Summing amplification part 7 1st monostable multivibrator 8 2nd monostable multivibrator 9 Power supply circuit part A 1st trigger input terminal B 2nd trigger input Terminal C ₇ Timer capacitor Q ₁ 1st output Q ₂ 1st inverted output Q ₃ 2nd output Q ₄ 2nd inverted output R ₁₄ Timer resistor R ₁₅ Timer resistor S Liquid crystal filter

Claims (1)

[Claims] 1. A direct current voltage is applied from a direct current power supply circuit to the summing amplifier, the first monostable multivibrator, and the second monostable multivibrator, respectively, and light is emitted by pulsed incident light including ambient light. A detection amplifier having a photodiode that generates a current and an amplifier that amplifies the photocurrent by voltage, a filter circuit that removes low frequency components from the output of the detection amplifier, and an AC output from the filter circuit. AC amplification section for amplifying the
And a summing and amplifying unit that adds and amplifies a predetermined voltage,
By inputting the first trigger pulse from the summing amplifier to the first trigger input terminal of the first monostable multivibrator and turning on the first trigger pulse, the first inverted output of the first monostable multivibrator is changed to the first inverted output. 2 trigger pulses
The second trigger input terminal of the second monostable multivibrator is applied, whereby the power supply output is applied from the second output of the second monostable multivibrator to the power supply circuit unit connected to the liquid crystal filter, By applying the output from the power supply circuit section to the liquid crystal filter, the dark state of the liquid crystal filter is maintained for a predetermined period of time determined by the timer capacitor and the resistor external to the second monostable multivibrator. In addition, the addition voltage to the addition amplification section is introduced from the second inverted output of the second monostable multivibrator. Control device.