JPH0261693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides two devices equipped with a device that damps vibrations when they come into contact with a filling in a container and drives or switches a display depending on the amplitude of the vibrations. It consists of a vibrating structure with vibrating elements, both of which have equal resonant frequencies, are fitted concentrically, and vibrate counter to each other in order to determine the height of the filling, and the outer vibrating element is , relates to a device for controlling the constant height of a filling in a container, formed as a vibrating rod extending into the container.

German Patent Application No. 2933618 discloses a system comprising two vibrating elements as rotary vibrators with equal resonant frequencies, fitted concentrically and oscillated in opposition, with the outer vibrating element extending into the container. The expanded device is shown. By arranging these two vibrating elements and properly distributing the mass, very little vibrational energy is transmitted to the walls of the container, so this vibrating structure can be used as a height control device. In this case, very high sensitivity can be obtained even for extremely lightweight packings. In addition, since only one vibrating rod is in contact with the filling, there is no drawback of the tuning fork type, which is caused by the filling getting stuck between the two rods and causing malfunction.

In the simplest configuration according to this West German patent application, two vibrating elements are arranged concentrically as rotating vibrators. The outer vibrating element is a tube extending into the container and fixed in the center of the membrane which acts as a return spring. The inner vibrating element is a rod projecting into the tube of the outer vibrating element, and this rod is fixed in the center of another membrane which likewise acts as a return spring. The outer edges of these membranes are fixedly connected to each other by tube pieces. Since these membranes together act as return springs, they also determine the frequency. Since the frequencies of both of the vibrating elements need to correspond to the membrane, high precision is required for machining the membrane. Furthermore, the external vibration element in this type of conventional device has a circular cross section. Therefore, when these conventional devices are installed on the wall of a container in the left-right direction, when the height of the filling material decreases, a large amount of powdered filling material such as flour will fall onto the vibrating element 1 as shown in FIG. As a result, the vibrating element 1 is damped and cannot resume vibrating, leading to malfunction of the device.

The filling material deposited on the vibrating element 1 can be shaken off by increasing the amplification factor of the device, allowing for precise control of the device, but this method allows for a lightweight filling material that is particularly suitable for this type of device. You can't control things.

The object of the invention is to provide a device of the above-mentioned type which is simple in construction and inexpensive to manufacture.
Particularly noteworthy is the configuration in which the internal vibration element does not require a membrane. Moreover, by using appropriate means, it is possible to eliminate malfunctions of the device due to the accumulation of filler material on the external vibration element.

According to the present invention, this problem can be solved by fitting two vibrating elements concentrically and making their resonant frequencies equal, so that the outer vibrating element is a rotating vibrator and the inner vibrating element is a bending vibrator. formed as,
The problem is solved by a vibrating structure that excites these vibrating elements in a counter-exciting manner to control the height of the filling. Preferably, the external vibration element is a tube extending into the container, closed at one end, and fixed at the other end in the center of the membrane, which acts as a return spring. On the other hand, the internal vibration element is preferably a cylindrical solid rod with one end protruding into the tube of the external vibration element and the other end fixed to a rigid plate. Furthermore, the plate is preferably connected to the outer edge of the membrane by a short cylinder, with which vibrations are coupled between the two vibrating elements.

According to this solution, the internal vibration element consists of only a simple rod, and no membrane is required as a return spring. Therefore, the structure is simple and can be manufactured at low cost. Furthermore, by making both vibrating elements appropriate dimensions and fitting them together like a telescope tube in a well-known manner, it is possible to equalize the resonant frequencies of both vibrating elements, and at the same time reduce the torque and mass deviation of both vibrating elements. Since the two vibrating elements compensate each other, the tube piece connecting both vibrating elements and the plate to which the internal vibrating element is attached can be maintained in a stationary state, thereby forming a node of the vibrating system. By means of this tube or via a vibration-isolating annular membrane connected to it, the vibrating structure can be moved to the wall of the container in the usual manner without the risk of vibrational energy being transmitted to said wall. Can be installed. In addition,
The cross-sectional shape of the external vibration element according to the present invention is not circular as in the conventional art, but at least its upper portion is wedge-shaped, so that the filler can easily slide down along the steeply sloped side. Also, make this contour symmetrical,
In other words, it may be wedge-shaped not only upwardly but also downwardly.

A sufficient space is defined inside the external vibrating element for the rod-shaped internal vibrating element to vibrate either as a bending vibrator or as a rotational vibrator as in the above-mentioned West German Patent Application No. 2933618. . A particularly simple and inexpensive method for obtaining such a special profile of the outer transducer is to press a tube of circular cross section into the desired shape. but,
It goes without saying that other methods can be used, such as welding or casting of shaped metal parts. According to the latter method, it is also possible to manufacture the entire external vibration element including the membrane and the screw-in piece as an integral component at low cost.

The vibration system is excited such that the vibration plane is perpendicular to the axis of the wedge. Due to this shape according to the invention, the effective surface for damping the vibrations caused by the filling is essentially enlarged compared to a vibration system with a circular cross section, and the sensitivity of the device is increased.

There are several suitable schemes for excitation and vibration measurements. Among them, the piezoelectric method was particularly advantageous. That is, in the piezoelectric method, two piezoelectric ceramic disks are arranged on the membrane of the external vibration element within the vibration plane, and are preferably bonded together. One of these ceramic disks acts as an excitation system. For this purpose, an alternating voltage is applied to the ceramic disk. The system is then excited because the diameter of this ceramic disk changes periodically, causing the membrane to deform accordingly. The other ceramic disc is used as a vibration measuring system, and due to the periodic deformation of the membrane during the vibration process a corresponding force acts on this ceramic disc, causing it to output an alternating voltage signal. This output signal is input to an amplifier in a well-known manner, and the amplified signal is input again to said one ceramic disk. At this time, if the phase relationship is appropriate and the loop amplification factor is 1 or more, it is possible to obtain a feedback system that vibrates like a conventional oscillator. As is well known, this system automatically vibrates at the resonant frequency of the mechanical vibrating structure. When the filling contacts a vibrating element extending into the container, its vibrations are damped and a threshold discriminator connected in series with the amplifier responds by switching, for example, a relay. When the height of the filling decreases and the vibrating element extending into the container is exposed again, the system resumes vibrating and the threshold discriminator switches the relay back to its original state.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of an embodiment of the device of the present invention. The device of FIG. 1 includes two vibrating elements,
These vibration elements are coaxially fitted together. That is, as an external vibration element extending into the container,
A tube 1 is fixed to the center of the membrane 3, and the membrane 3
acts as a return spring. This external vibration element rotates and vibrates about the central axis of the membrane 3. On the other hand, the internal vibration element is comprised of a cylindrical rod 2 inserted into the tube 1 of the external vibration element and attached to a solid, rigid plate 4.
This rod 2 is fixed at one end, causing bending vibrations of the rod. The outer edge of the membrane 3 is fixed by a tube 5 to the plate 4, on which the rod 2 is attached. Inside the membrane 3, two piezoelectric ceramic discs 6, 7 are arranged diametrically opposite each other in the plane of vibration. These piezoelectric ceramic disks 6, 7 act as an excitation and vibration measurement system. When an alternating current voltage is applied to the piezoelectric ceramic disk 6, its diameter changes periodically, and the membrane 3 deforms each time. In a certain phase of the AC voltage, the diameter of the disk 6 increases, the membrane 3 deforms, and the tube 1
is driven in the direction of arrow A in the figure. In the opposite phase, the diameter of the disk 6 is reduced, the membrane 3 is deformed and the tube 1 is driven in the direction opposite to arrow A in the figure. As a result, the tube 1 vibrates in the left-right direction within the plane of the figure with the center C of the membrane 3 as an axis. This vibration becomes a rotational vibration in which all points on the tube 1 move simultaneously at the same angle with respect to the axis C. At this time, the membrane 3 acts as a return spring.

When the external vibration element consisting of the tube 1 and the membrane 3 starts to vibrate, this vibration is transmitted to the plate 4 supporting the rod 2 through the tube 5, and an alternating current torque acts on the plate 4. As a result, the plate 4 excites a bending vibration that causes the rod 2 to vibrate in the left-right direction within the plane of the figure. Bending vibration is a vibration in which the deflection is nonlinear, and the deflection angle increases as the distance from the fixed point increases. When the tube 1 is driven in the direction of the arrow A in the figure, the vibration of the rod 2 becomes a vibration that is counter-driven in the direction of the arrow B in the figure with the tube 5 as a node of the vibration system. It should be noted that sufficient space is provided inside the tube 1 for the rod 2 to vibrate in opposition to the tube 1. Due to the above-mentioned periodic deformation of the membrane 3, an alternating force acts on the other piezoelectric ceramic disk 7 during the vibration process, so that the disk 7 receives an alternating voltage corresponding to the amplitude and frequency of the mechanical vibration. Occur. This AC voltage is input to an amplifier 11 and amplified, and the output of this amplifier 11 is input to a piezoelectric ceramic disk 6 which acts as an excitation system.
Therefore, if the loop amplification factor is 1 or more, a feedback system that automatically vibrates at the resonant frequency of mechanical vibration can be obtained. When the vibration system vibrates at a threshold value, a discriminator 12 connected in series with the amplifier 11
responds to this and switches relay 13. As mentioned above, both vibrating elements 1 and 2 have the same resonant frequency and vibrate opposingly, so the two types of torque generated by both vibrating elements compensate each other during the vibration process, and both vibrating elements are dimensioned so as to compensate for the effects caused by the vibrational deviation of their masses, so nodes of the vibration system are formed in the tube 5,
The center of gravity of the entire system and the tubes 5 and plates 4 are kept stationary during the vibration process.

FIG. 1 further shows a state in which an annular membrane 8 is provided on a screw-in piece 9 screwed into the wall 10 of the container.

Further, FIG. 2 shows an example of the external vibration element 1 having a circular cross section, in which a powdery filler 14 such as wheat flour is filled.
After the height of the filling 14 is reduced, the filling 14 may remain in the form of a plate, in which case the system is damped and cannot resume oscillation, and the device gives a false indication. It is.

On the other hand, FIGS. 3 and 4 are cross-sectional views showing a vibrating element 1 according to an embodiment of the present invention, which is wedge-shaped upward so that the filling can easily slide down the side surface. There is. In this case, for reasons of symmetry, the vibrating element 1 is wedge-shaped even when facing downward. Further, inside the vibrating element 1, a margin is provided for a rod 2 that vibrates in opposition.

Figure 3 shows an embodiment that can be manufactured by casting;
The figure shows an embodiment obtained, for example, by welding two half-tight shells or, particularly preferably, by pressing a tube of circular cross-section. It will be clear that, according to the shape of the invention, the effective surface for vibration damping of the filling is enlarged, resulting in an increase in the sensitivity of the device.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a cross-sectional view for explaining the drawbacks of the conventional device, and FIGS. 3 and 4 are cross-sectional views showing different embodiments of the present invention. 1...Pipe (external vibration element), 2...Rod (internal vibration element), 3...Membrane, 4...Plate, 6, 7...
Piezoelectric ceramic disc.

Claims (1)

[Claims] 1. The vibrations are attenuated when they come into contact with the filling in the container, and the display is driven according to the amplitude of the vibrations,
or a filling in a container consisting of a vibrating structure having two vibrating elements equipped with means for switching, both vibrating elements being fitted concentrically and having equal resonance frequencies and opposing vibrations; A device for controlling the height of a filling in a container, characterized in that an outer vibrating element is formed as a rotating vibrator, and an inner vibrating element is formed as a bending vibrator. A device to control. 2. The outer oscillating element consists of a tube 1 which extends into the container and is closed at one end, while the other end is fixed in the center of a membrane which acts as a return spring, and the inner flexural oscillator is , one end of which is fixed to a rigid plate 4, vibrates at its resonant frequency when excited, and forms a rod protruding into the tube 1, and the plate 4 is connected to the tube 5.
2. The apparatus according to claim 1, wherein the vibration element is coupled to the outer edge of the membrane 3 to form a vibration coupling body of both vibration elements. 3. The torque and mass deviation of both vibrating elements are compensated for each other by the vibration process of both vibrating elements, and the tube 5 connecting both vibrating elements forms a node of the vibrating system and is maintained in a stationary state. The device according to claim 1 or 2, characterized in that both vibrating elements are dimensioned and fitted over such a distance. 4. Device according to any one of claims 1 to 3, characterized in that piezoelectric ceramic discs 6, 7 are arranged on the membrane 3 for excitation and vibration measurement. 5. The electric signal of the piezoelectric ceramic disk 7 can be input to the amplifier 11, and the output signal of the amplifier 11 can be input to the other piezoelectric ceramic disk 6 and the threshold value discriminator 12 that drives the relay. An apparatus according to any one of claims 1 to 4. 6. A vibrating structure that damps vibrations when it comes into contact with the filling, and this vibrating structure is composed of a tubular external vibrating element extending into the container and a rod-shaped external vibrating element protruding into the recess of the external vibrating element. Consisting of an internal vibration element,
A device for equalizing the resonant frequencies of these two vibrating elements and controlling the height of the filling in the container formed as an opposing rotational vibrator and a bending vibrator, at least on the top side of the external vibrating element. 1. A device for controlling the height of a filler in a container, characterized in that the filler is formed into a wedge shape so that the filler easily slides down the side of the container. 7. The device according to claim 6, wherein the external vibration element is wedge-shaped at the upper and lower sides. 8. The device according to claim 6 or 7, characterized in that the contour of the external vibration element is obtained by press-molding a tube with a circular cross section.