JPS606827A - Liquid level detector - Google Patents

Abstract

PURPOSE:To improve detection precision by moving up and down periodically a ferromagnetic body or float which turns on and off a microswitch and detecting the lower limit of a level only at a break position. CONSTITUTION:A frame 19 is fitted to the wall 11 of a solder tank 10, a rack 20 is projected from the frame to over the solder tank, and a dog 17 is fixed in a position adjustable state. The float 15 floats on the fused solder in the solder tank 10 and fluctuates according to the level 12 of the solder tank. The dog 17 is hooked to the lever 14 of the microswitch 13 and moves up and down together with the float 15 to turn on and off the microswitch 13. When the level 12 of the fused solder is even a little bit lower than the lower limit, the microswitch 13 is left on because the contact of the microswitch 13 is not permitted to go beyond the break point.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an improvement in a level detection device consisting of a float floating in a liquid tank and a microswitch that opens and closes depending on whether the float is up or down.

<Prior Art> Level sensing devices are used to maintain a constant level in a liquid tank. For example, in a solder tank level detection device consisting of a flow I and a microswitch, when the level falls below the lower limit, the float pushes the lever of the microswitch to start the solder supply device and replenish a certain amount of solder into the solder tank. and maintain the level. However, the contact point of a microswitch has a difference between the make position where it goes from off to on and the break position where it goes from on to off, and the level detection signal is generated in the contact area between the make position and the break position, so the break position and the make position are different. Detection errors due to differences in position could not be avoided. Moreover, the difference was amplified by the lever, so it was not possible to accurately detect the lower limit of the level. For example, in order to perform high-precision soldering on precision printed circuit boards, it is necessary to suppress the lower limit error of the solder bath level within 0 to 0.3 + nm, but conventional floats and level detection methods such as Microsui and Sochi cannot be used. Since the device had poor level limit detection accuracy, it was impossible to keep the lower level accuracy within 0.3 mm.

<Objective of the Invention> The present invention seeks to provide a device for detecting the level of a liquid tank with high accuracy.

<Structure of the Invention> In order to achieve the above object, the device of the present invention includes a frame mounted on a liquid tank, a microswitch fixed to the frame, a float floating on the liquid tank to turn on and off the microswitch, It consists of an electromagnet that operates periodically, a ferromagnetic material that is moved up and down by the electromagnet to turn the microswitch on and off, and a circuit that extracts the microswitch's on signal.The circuit receives the microswitch's on signal during the period when the electromagnet is not acting. Take it out only inside.

When a ferromagnetic material such as a permanent magnet is attached to the tip of the float's shaft, the periodically operating electromagnet will periodically push down the float via the permanent magnet fixed to the flow. Make sure to turn the switch from off to on. The lower limit of the level should match the break position of the microswitch contact. If the level is above the lower limit, the electromagnet stops operating and the float floats.1. Since the microswitch changes from on to off, the microswitch signal that the circuit picks up when the electromagnet is not activated is off and no level sensing is performed. However, if the level falls even slightly below the lower limit, the microswitch remains on even after the electromagnet is activated, so the circuit picks up the on-signal from the microswitch and detects the level. In this way, the magnet of the present invention detects the level only by the break position of the microswitch contact, and unlike conventional devices that detect the level in the contact area between the break position and the make position, the magnet of the present invention has a high level detection accuracy. It becomes clear and high.

In addition, in accordance with the delay from the time when the electromagnet stops operating until the float floats freely, the starting point of the period in which the circuit picks up the microswitch signal also coincides with the time when the electromagnet stops operating.
It is desirable to extend it slightly immediately after.

<Example> The apparatus of the present invention will be explained based on embodiments shown in the drawings.

As shown in FIG. 1, a frame 18 is attached to the tank wall j1 of the solder tank lo, and a pedestal 2° is projected from the frame onto the solder tank. Attach the guide 21 to the tip of the pedestal 2o,
The shaft rod 16 of Flow) 15 is inserted into the guide 21 so that it can be moved up and down. A dog 17 is fixed to the upper end of the shaft rod 16 so that its position can be adjusted. Flow) 15 floats on the molten solder in the solder bath lO and rises and falls with the level 12 of the solder bath. dog 17
is applied to the microswitch 13 and moves up and down together with the float 15 to turn the microswitch 13 on and off. The arm 18 protrudes from the top of the frame 19,
An electromagnet 23 is attached to the arm. On the other hand, float 1
A permanent magnet 22 is attached to the tip of the shaft rod 16 of No. 5. When the electromagnet 23 is energized and excited, as shown by arrow A,
The permanent magnet 22 repulses and lowers the float 15 to a predetermined position. At that position, the dog 17 pushes down the lever 14 to the make position that changes the contact point of the microswitch 13 from off to on, thereby turning it on securely. When the electromagnet 23 is de-energized, the float 15 is lifted by the buoyancy of the molten solder, as shown by arrow B. If the level 12 is above the lower limit, the contact of the microswitch 13 is turned off because it exceeds the break position where it changes from on to off. However, level 12
If is even slightly below the lower limit, the lever 14 will not allow the contact of the microswitch 13 to exceed the break position, so the microswitch 13 will remain on.

As shown in FIG. 2, when the push button FBI of the device of the present invention is turned on, the self-holding relay R1 is energized and the circuit is self-holding. At the same time, the timer T relay, which repeats on and off at an adjustable constant cycle, is also energized.

When the timer T is turned on, the DC solenoid 23 and the coil of the time-limited return relay R2 are energized, and the relay R2 is turned off. While the timer T is on, the magnetic force of the excited electromagnet 23 and the magnetic force of the permanent magnet 22 attached to the tip of the shaft 16 of the float 15 repel each other, so the float 15 remains in the solder bath 1o.
Since the dog 17 lowers the contact point of the micro switch 13 to the make position via the lever 14, the micro switch 13 is surely turned on. However, since relay R2 is off, the coil of relay R3 of the level detection signal generation circuit (not shown) is not excited, so no level detection signal is transmitted. When the timer T is turned off, the electromagnet 23 is demagnetized and the force pushing down the permanent magnet 22 disappears, so the float 15 floats upward. At the same time, the coil of time-limited return relay R2 is also demagnetized, so relay R2 is turned on. The delay time from when the timer T is turned off to when the relay R2 is turned on is set to be longer than the time until the float 15 is fully floated. At this time, if the level 12 of the solder bath 1o is higher than the lower limit, the microswitch 13 is turned off, so the relay R3 is not excited and no level detection signal is transmitted. However, if the level 12 of the solder bath 10 is at or even slightly below the lower limit, the contacts of the microswitch 13 will not reach the break position, so the microswitch 13 will remain on. As a result, relay R3
The coil is excited and a level detection signal is transmitted. Although not shown, when the level detection signal is transmitted, the solder supply device is activated and supplies a certain amount of solder to the solder tank to maintain the level of the solder tank within a predetermined range. In addition, the button P
Pressing B2 will disconnect the circuit and stop the device.

As shown in FIG. 3, a permanent magnet 22 may be fixed to one end of a lever 24 pivoted to the frame 18, and an electromagnet 23 may be attached to the frame 19 above the permanent magnet. Electromagnet 2
3 is activated, the permanent magnet is attracted and rises, and the other end of the lever 24 pushes down the lever 14 of the microswitch 13 to turn on the microswitch. Other than the above-mentioned differences, the embodiment of FIG. 3 is exactly the same as the previous embodiment.

The timer for this circuit can be of any type, such as a CR timer consisting of a resistor and a capacitor, or an electronic timer that uses the commercial frequency as a clock pulse, but the on/off cycle of the timer depends on the solder bath. It is desirable that soldering be adjustable according to the work cycle. Although the embodiment has been shown only with respect to a solder bath, it goes without saying that the apparatus of the present invention is not limited to a single solder bath, and can be applied to any liquid bath.

<Effects of the Invention> As stated, the device of the present invention can set the lower limit of the level only at the break position of the microswitch by periodically lowering the ferromagnetic material or float that turns the microswitch on and off. Unlike conventional devices that detect in the area between the break contact and make contact of a microswitch, there is no accuracy defect due to the difference between the break contact and the make contact. Therefore, the detection accuracy is significantly improved compared to the conventional one. The mechanism for raising and lowering the ferromagnetic material or the float is electromagnetic, and the device has no mechanically moving parts, so it has a simple structure and excellent durability.

[Brief explanation of the drawing]

Figure 1 shows the main components of a soldering bath equipped with an apparatus according to an embodiment of the present invention.
A partial sectional view, FIG. 2 is a schematic diagram showing the circuit of the device of FIG. 1, and FIG. 3 is a diagram corresponding to FIG. 1 of another embodiment. In the figure, 10 is a solder tank, 12 is a level, 13 is a micro switch, 15 is a float, 16 is an axis rod, 17 is a dog, 19 is a frame, 22 is a permanent magnet (ferromagnetic material),
23 is the electromagnet applicant Matsuo Handa Co., Ltd. Figure 1 Figure 18 No. 2 Procedural Amendment July 18, 1980 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office 1. Indication of the case 1988 Patent Application No. 112776 2. Invention Name Liquid Level Detection Device 3, Person making the amendment Relationship to the case Patent applicant Name Matsuo/\Da Co., Ltd. 4, Agent 5, Date of amendment order Voluntary action 6, Number of inventions increased by the amendment None Contents (1) The scope of claims is amended as follows. l) The frame taken into the liquid tank and the frame 1/-18
It consists of a microswitch fixed to the liquid tank, a float equipped with an I-lug that floats on the liquid tank and turns the microswitch on and off, and a circuit that detects the operation of the microswitch. When the limit is turned off, the tongs actuate the microswitch to detect the level, and the tongs operate the microswitch periodically to turn it on and off by periodically raising and lowering the microswitch by the operation of the electromagnet and the electric current. a ferromagnetic material that causes the electromagnet to move, and the circuit extracts the signal from the microswitch only during a period when the electromagnet does not move f1. 2) The liquid level detection device according to claim 1, wherein the ferromagnetic material is previously installed on the float. 3) A patent claim characterized in that an ON signal of the microswitch is obtained during a period from a predetermined time after the electromagnet stops the operation of lowering the ferromagnetic material until the operation is heard. The liquid level detection device according to item 1 or 2. (2) On page 4, line 4, line 5 of the specification, ``When the tip is attached'' is corrected to ``If you can reach the tip.'' Hand Thread Sales Supplement T1 Book 1811158 August 1311 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the Case Patent Application No. 112776/19822, Name of the Invention Still Image Level Detection Device 3, Person Making the Amendment Relationship with the Case Patent applicant name Matsuo Handa Co., Ltd. 4, Agent 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment None 1, Dai LIJ
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Claims (1)

[Scope of Claims] 1) A frame attached to a liquid tank, a microswitch fixed to the frame, a float equipped with a dog that floats on the liquid tank and turns the microswitch on and off, and the microswitch. The device includes a circuit that detects the operation of a switch, and when the level of the liquid tank falls below the lower limit, the dog activates the microswitch to detect the level, and the device includes an electromagnet that operates periodically, and a circuit that detects the level of the electromagnet. a ferromagnetic material that periodically moves up and down upon activation to turn on and off the microswitch, and the circuit extracts an ON signal from the microswitch only during a period when the electromagnet is not activated. Device. 2) The liquid level detection device according to claim 1, wherein the ferromagnetic material is attached to the float. 3) The on-signal of the microswitch is obtained during a period from the time when the electromagnet stops moving the ferromagnetic material up and down until it resumes operation after a predetermined period of time has elapsed. The liquid level detection device according to item 1 or 2.