JPH0428028Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application: The present invention relates to a liquid level detection device for a cassette-type tank used, for example, in an oil fan heater, an oil stove, or a humidifier.

Problems to be Solved by the Prior Art and Ideas: As a conventional liquid supply device using this type of cassette type tank, a type whose main part is shown in FIG. 3 is known. Specifically, numeral 1 is a cassette type tank which is a container for liquids such as petroleum, water, etc., and 2 is an injection cap for injecting liquid C into the tank 1, which is screwed into an opening at the bottom of the tank. Reference numeral 3 denotes a valve stem located at the center inside the injection cap 2. When the tank is closed, the inner cover presses the inside of the injection cap 2 with a spring 3b, and the valve 3a closes the bottom of the tank. Liquid conveyance path 1
The filling cap 2 of the tank is liquid-tightly fitted into the tank support part A forming a part of the tank support part 4 via the rubber bushing 15, and the saucer 5 has a valve holding rod 4 for opening the valve in the center. When the valve is fitted, the valve presser rod 4 pushes up the inner lid against the spring 3b, opening the injection cap 2 and opening the valve 3a, allowing the liquid in the tank to fall, and directing it toward the saucer 5. The liquid then flows out as shown by the arrow and reaches the liquid transport section. A part of the side wall of the tank 1 is cut out and a glass window B is vertically installed from the bottom to approximately 2/3 of the height, so that the liquid level can be visually observed from the outside. This configuration has disadvantages in that the cost of molding the glass window is high, and that it is sometimes difficult to capture the liquid level during use due to fogging and dirt, making it impossible to monitor the liquid level sufficiently.

Means for solving the problems: This proposal is a proposal to solve these problems, and its structure is to install a valve stem in a closable manner through the injection cap of a cassette-type tank, and to attach it at the upper end. The lower end of the valve holding rod that opens the valve passes through the bottom wall of the valve receiving chamber of the tank support part A, which forms the starting point of the liquid conveyance path, and is fixed. A piezoelectric element is attached to the lower end surface. A bush made of an elastic material having a low Q value (low vibration transmission rate) such as silicone rubber is fixed to the bottom wall through the bottom wall. The vibrations generated by the piezoelectric element are thereby cut off from leaking to the bottom wall of the tank support A.

Action: By applying an alternating voltage with a predetermined resonance frequency to the piezoelectric element, the ultrasonic waves generated are transmitted to the valve holding rod and the valve stem, and are transmitted from the tip of the valve stem toward the liquid level L in the tank. The ultrasonic wave, that is, the reflected wave that is emitted and reflected back from the liquid surface L, is received at the tip of the valve stem, propagated from the valve stem to the valve holding rod, and extracted as an electric signal from the piezoelectric element, By measuring the time from when an ultrasonic wave is emitted from the piezoelectric element to when the ultrasonic wave is reflected back from the liquid surface L and is received, the liquid level H and the amount of liquid in the tank can be detected.

Example: An example will be described based on FIGS. 1 and 2. Note that the same parts as those shown in FIG. 3, which is a conventional example, will be described with the same reference numerals. In the figure, 4 is a valve holding rod, but unlike the one shown in FIG. It is liquid-tightly fixed to the through hole 8 by a bushing 9 made of an elastic material such as silicone rubber.
6, and a piezoelectric element mounting plate 10 is provided thereon,
An ultrasonic vibrator or piezoelectric element 11 made of piezoelectric ceramic such as lead zirconate titanate is integrally attached thereto by bonding means (not shown) such as adhesive or bolts. The surface of this piezoelectric element 11 is provided with an electrode 12 made of silver vapor deposition, silver plating, etc., and this electrode 12 is connected to a level detection circuit 13 including an ultrasonic transmitting circuit and a receiving circuit provided adjacently.
The valve receiving chamber 7 is also a conveyance path for the liquid flowing out from the cassette type tank, and in the case of a kerosene stove, it conveys fuel to the combustion chamber, and in the case of a humidifier, conveys water to the atomization chamber.

Effects: This invention has a cassette tank with the same structure as the conventional one.
The structure of the valve holding rod was improved by using parts such as the injection cap and valve stem, and the lower end mounting plate was protruded outside the bottom wall of the valve receiving chamber, and a piezoelectric element was added to this, and the generated ultrasonic waves were The valve presser rod and the valve stem itself are used as vibration propagating members, and no special new propagating members are added. The valve holding rod was fixed to the through hole in the bottom wall using a bushing such as silicone rubber with a low Q value, so the vibration of the piezoelectric element could be clearly fixed without leaking to the bottom wall of the valve receiving chamber of the tank support. It enables liquid level L detection and flow rate measurement, and measurements with excellent conversion efficiency can be performed. In this way, the problems with visual inspection and monitoring caused by conventional glass windows can be solved.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of the main parts showing one embodiment of the liquid level detection device of the present invention, Fig. 2 is a perspective view of the main parts of the invention in which a piezoelectric element is attached to the valve holding rod, and Fig. 3 is a FIG. 1 is a longitudinal cross-sectional view of a conventional liquid level detection device. 1...Cassette tank, 2...Injection cap,
3...Valve stem, 4...Valve holder rod, 5...Saucer, 6
...Bottom wall, 7...Valve receiving chamber, 8...Through hole, 9...
Elastic adhesive bush, 10...Mounting plate, 11...
Piezoelectric element, 12...electrode, 13...level detection circuit, 14...liquid conveyance path, 15...rubber bush, 16...vacancy, A...tank support, B...
Glass window, C...liquid, H...height to liquid level,
L...Liquid level.

Claims (1)

[Scope of utility model registration request] In a liquid supply device that opens at the upper end of a valve rod installed in an injection cap at the bottom of a cassette type tank and a valve holding rod installed in a valve receiving chamber that supports the tank,
The valve holding rod is fixed by liquid-tightly fitting the bottom wall of the valve receiving chamber with a bush made of a low Q material, and a piezoelectric element is attached to the lower end of the valve receiving chamber projecting outwardly, Furthermore, the piezoelectric element includes a transmitting circuit that emits ultrasonic waves into the liquid in the tank through the valve holder rod and the valve stem, and a transmission circuit that emits ultrasonic waves that are reflected by the liquid surface and returns through the valve holder rod and the valve stem. A liquid level detection device, characterized in that a liquid level detection circuit including a receiving circuit for converting into a signal is connected to the liquid level detection circuit.