JPS604820A - Small sized vibration type level detector - Google Patents

Abstract

PURPOSE:To obtain a small level detector excellent in the stability by having a diaphragm vibrating in resonance with a piezo-electric element provided on the back thereof to detect changes in the vibration amplitude due to a powder, particulate, liquid or the like contacting the surface of the diaphragm through a vibro-voltage conversion element. CONSTITUTION:A level detector is made up of a diaphragm 1, a vibrating piezo- electric element 3, a vibro-voltage conversion element 3', a weight 4 and electrodes 5a-5c all arranged on a circular frame 2. The surface of the diaphragm 1 is mounted facing the inside of a container 6 and an object 7 to be inspected such as a powder, particulate and liquid is fed to the container 6. An AC voltage is applied to the piezo-electric element 3 through the electrode 5b to vibrate in resonance the diaphragm 1 and changes in the vibration amplitude generated upon the contact of the object 7 being inspected with the diaphragm 1 are converted into an electrical signal through the electrodes 5a and 5c and the vibro- voltage conversion element 3' to detect level changes of the object 7 being inspected. Thus, a small level detector is obtained with an excellent stability.

Description

DETAILED DESCRIPTION OF THE INVENTION (]) LI aspect of the invention The present invention relates to a small vibrating one-novel detector for detecting level changes of powder, granules, liquid, etc. in a container.

A conventional vibrating level detector has a structure as shown in Fig. 1, and detects the detected object such as powder most efficiently when the diaphragm 1' vibrates at a mechanical resonance point. be able to.

However, in order to manufacture a compact conventional detector, the diameter of the diaphragm plate 1' must be made small, and as the diameter of the diaphragm l/ is made small, the natural resonant frequency becomes high and the vibration amplitude increases. is expected to decrease, therefore,
If the resonance point is in the audible frequency range, the sound will be very harsh to the ears. When the amplitude decreases, the detection sensitivity becomes too high, which makes the operation unstable and susceptible to external vibrations, etc. Moreover, it eliminates powder and viscous liquid that adhere to the detection surface of the diaphragm P. Since the power is also weakened, various defects arise that can cause malfunctions.

As a means of lowering the resonance frequency &, one method is to reduce the thickness of the diaphragm 1' or to use a material with low elasticity, but this inevitably involves a decrease in strength.

The disadvantage of using a method other than driving at a resonant frequency is that if you want to increase the amplitude, you need to strengthen the 7111 vibration, and as a countermeasure for the sound at a frequency that is unpleasant to the ear, you can lower the volume. Alternatively, is there a method using ultrasonic waves? There are disadvantages such as being easily affected.

The purpose of the present invention is to eliminate the disadvantages of the conventional dual-unit type level detector, and to provide a small level detector with excellent operational stability even with a small diameter diaphragm, and which does not emit harsh sound. The price is on offer.

(2) Structure of the Invention In the small vibrating level detector according to the present invention, an alternating current voltage is applied to the excitation piezoelectric element on the back side of the diaphragm to cause the diaphragm to resonate, and powder is applied to the surface of the diaphragm. In a vibrating level detector that detects level changes in powders, granules, liquids, etc. by converting changes in vibration amplitude caused by contact with powders, granules, liquids, etc. into electrical signals using an oscillating voltage conversion element,
It is characterized by a configuration in which a weight is attached to the diaphragm to vary the resonance frequency.

To explain the drawings of the embodiment below, 1 is shaken,
A vibrating piezoelectric element 3 such as a piezoelectric magnetic plate is attached to the back surface in a predetermined manner. 3' is a vibration voltage conversion element 0, 4 is a cylindrical weight, and inside the annular frame 2, a diaphragm 1, an excitation piezoelectric element 3. It is connected to the oscillating voltage conversion element 3'.

Reference numeral 6 denotes a container in which the object to be detected is supplied, and when the detector of the present invention is used, the surface of the diaphragm 10 is directed into the container 6, and the flange portion 2f of the annular frame 2 is in contact with the outer wall surface of the container 6. Attach to.

A detected object 7 such as powder, granules, or liquid is supplied into the container 6. When an AC voltage is applied to the excitation piezoelectric element 8 to cause the diaphragm 1 to resonate, the diaphragm 1 Object to be detected 7 on the surface of
Since a change in the vibration amplitude occurs due to the contact, this change in vibration amplitude is converted into an electric signal by the vibration voltage conversion element 8' to detect a change in the level of the object to be detected 7 in the container 1. However, since the weight 4 is fixed at the center of the diaphragm 1, the frequency of the resonance vibration is reduced. This reduction rate can be set to an arbitrary value by adjusting the weight of the single weight 4.

(3) Effects of the Invention In the detector of the present invention, the weight 4 for lowering the resonance frequency is attached to the center of the diaphragm l, so that the following effects are derived.

First, when vibrating at a low frequency, vibrations with a larger amplitude can be obtained than when vibrating with the same driving force as a conventional diaphragm. Therefore, when used for detecting the upper limit of the detected object 7 in the container 6, if there is a rigid object (
It has the advantage of being easy to remove (powders and viscous liquids). Furthermore, as an effect on the auditory sense of vibrational sound, an experimental result was obtained that the vibrational sound is alleviated to the extent that it can be endured for a long period of time if the sound has a frequency of 800 Hz or less.

Second, when driven at the resonant frequency, efficient vibration can be obtained with less driving force than in the past, and powders and liquids can be detected with high sensitivity.

As the piezoelectric element 8 for vibration, even a weak excitation force of the ff electromagnetic plate can be used, so it can be manufactured at low cost, and the drive voltage can be lowered, which has the advantage of reducing maintenance costs. be.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a conventional vibrating level detector. Figure 2 is a longitudinal cross-sectional view of the detector of the present invention, and Figure 8 is A of Figure 2.
- Cross-sectional view taken along line A. (A) CB) (C) CD) of FIG.
(A) and (CB) in the figures are back views of the diaphragm illustrating the arrangement of the vibration piezoelectric element and the oscillating voltage conversion element in the detector of the present invention. FIG. 6 is a longitudinal cross-sectional view illustrating the mounting state of the detector of the present invention when in use. ■--Vibration plate, 3... Piezoelectric element for vibration, 8'...
Vibrating voltage conversion element, 4... weight. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A piezoelectric element (3) for vibration is fixed on the back side of the diaphragm (1),
An alternating current voltage is applied to the piezoelectric element (3) for vibration, and the diaphragm (
+1 is resonantly vibrated, and the change in vibration amplitude caused by contact of powder, antibody, liquid, etc. with the surface of the diaphragm (1) is converted into an electric signal by a vibration voltage conversion element, and the powder, granule, etc. A small vibrating level detector for detecting level changes in liquid, etc., characterized in that a weight (4) is attached to a vibrating plate (1) to make the resonance frequency variable. .