Liquid level sensor

Measuring and testing – Liquid level or depth gauge – Thermal type

Patent

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Details

338226, 338229, 374185, G09F 2324, H01C 102, G01K 722

Patent

active

059101890

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention is related to a liquid level detector for detecting the changing level of liquid.


BACKGROUND OF THE INVENTION

Liquid level detectors have widely been used in various liquid tanks, for example, in an automobile for detecting the changing level of fuel in a tank.
A conventional liquid level detector is comprised of a cylinder-shaped thermistor having electrodes at both ends, provided with metal caps at both ends, each of the caps being connected with a lead wire, the entire structure being stored in a cylindrical metal case, the lead wires being taken out of the metal case from both ends. The changing level of a liquid is detected by applying a voltage to the thermistor and reading a change in the resistance of the thermistor caused by shift in the height of a liquid level.
A problem in the above described structure is that a cap has to be thrusted to cover an electrode of thermistor for taking out a lead wire, and the lead wire has to be soldered to a metal case; these brings about a complication in assembly process.


DISCLOSURE OF THE INVENTION

The present invention is intended to present a liquid level detector which does not require any soldering process in the assembly and the assembly work therefor is easy.
A liquid level detector according to the present invention comprises an open metal case with a bottom having at least one through hole, an element holder stored in the metal case, a thermistor having electrodes at both ends and seated on the element holder, a terminal electrically coupled in one end with the thermistor, a coil spring disposed around the terminal for fixing the terminal, a terminal member electrically coupled with the other end of said terminal, and an insulator having at least one through hole, for holding the terminal member as well as for closing the opening of said metal case.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a liquid level detector according to a first embodiment of the present invention.
FIG. 2 is a side view of an element holder used in the liquid level detector of FIG. 1.
FIG. 3 is a cross sectional view of the element holder in the bottom portion.
FIG. 4 is a plane view of an insulator used in the liquid level detector of FIG. 1.
FIG. 5 is a cross sectional view of a liquid level detector according to a second embodiment of the present invention.
FIG. 6 is a cross sectional view of an element holder used in the liquid level detector of FIG. 5.
FIG. 7 is a plane view of an insulator used in the liquid level detector of FIG. 5.


DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of a liquid level detector according to the present invention will be described in detail with reference to drawings.
In a liquid level detector according to a first embodiment of the present invention as shown in FIG. 1 through FIG. 4, a cylinder-shaped metal case 1 is made of brass plated with Ni for anticorrosion, having a bottom, and at the opening edge of which case a fitting portion 1a is provided. In addition, the metal case 1 is provided with three through holes(not shown) in the bottom on a concentric circle at an equal spacing, so as liquids can freely flow in and out the metal case 1. At least one such through hole may suffice, and, such hole may be disposed in the side wall of metal case 1.
An element holder 2 is made of a metal having low thermal conductivity and anticorrosion property, such as a stainless steel, and comprises an electrode 2a to accept thermistor 7 and a foot(supporting portion) 2b. The foot 2b is provided with a fitting portion 2c. The electrode 2a is formed in a counter-position to an electrode 3a of terminal 3 after assembly. The electrode 2a is provided with a protrusion at the bottom for ensuring a good contact with an electrode surface of thermistor 7, as well as a small through hole 2d in the centre of protrusion, the diameter of which hole being smaller than thermistor 7, to assure a good dripping of liquid, as shown in FIG. 3. Around the electrode 2a, a hollow

REFERENCES:
patent: 3044296 (1962-07-01), Boddy
patent: 3890588 (1975-06-01), Kanaya et al.
patent: 3918018 (1975-11-01), Tuley et al.
patent: 3919680 (1975-11-01), Ueno et al.
patent: 4065760 (1977-12-01), Feldon
patent: 4318073 (1982-03-01), Rossler, Jr. et al.

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