KR100781199B1 - Vibratory level sensor - Google Patents

Abstract

While preventing malfunction due to dust adhering to the upper side of the vibrating rod, the two thin-film supports can stably support the rod while actively suppressing the damping amount of vibration, and can be easily assembled. The level sensor includes a rod 8 and a rod 8 having a proximal end and a proximal end free of end, with the distal end entering the storage container 20 of the object to be charged 13. ) Between the exciters 14A and 14B for adding vibration to the support), the support bodies 4 and 9 of the circular thin film-like support for supporting the rod 8 at two places serving as the nodes of the vibration, and both nodes of the rod 8. It is provided with a cylindrical protective tube (7) covering. One support 4 is fitted and fixed to one end inner surface of the protective tube 7, and the other support 9 has a larger diameter than the one of the support 4, and the other of the protective tube 7 Fix it against the end face. The support body 4 close to the location where the exciters 14A and 14B are mounted in the rod 8 sets the thickness thicker than the other support body 9.

1st support body, protection tube, rod, 2nd support body, to-be-filled object, piezoelectric element (vibrator), storage container

Description

Vibratory Level Sensor {VIBRATORY LEVEL SENSOR}

1 is a longitudinal sectional view showing a level sensor according to a first embodiment of the present invention.

FIG. 2 is a plan sectional view of the main portion of the level sensor of FIG.

3 is a block diagram illustrating a driving circuit unit for the level sensor of FIG. 1.

4 is a plan view illustrating the action of the rod in the level sensor of FIG.

5A to 5F are planar cross-sectional views sequentially illustrating a manufacturing process of the level sensor of FIG. 1.

It is a longitudinal cross-sectional view which shows the level sensor which concerns on 2nd Embodiment of this invention.

7 is an enlarged left side view of the level sensor of FIG.

8 is a left side view showing the rod of the level sensor of FIG.

It is a left side view of the rod which shows the modification of 2nd Embodiment.

The present invention relates to a vibrating level sensor that detects whether a to-be-filled object has been filled to a predetermined height level, for example, when a to-be-filled object such as powder, powder or liquid is filled into a storage container such as a tank.

Conventionally, as this type of vibrating level sensor, what is described in Japanese Unexamined-Japanese-Patent No. 62-293127 as a filling surface adjustment apparatus is known. This apparatus uses a vibration rod having a piezoelectric element attached to one end of a band-shaped metal vibration piece at two places where the vibration node of the primary vibration mode appears. Each support is elastically supported by a support made of a thin film, and both supports are attached by welding to openings at both ends of a cylindrical protective tube covering both nodes in a vibration mode, and the other ends of the vibration rods protruding from the protective tube are The piezoelectric element and the mass are attached. This mass is provided in order to shorten the period of vibration and to increase the amplitude of the measurement probe to improve the detection accuracy of the object to be filled.

When the filling surface of the to-be-filled object which rises with the filling operation | movement to a storage container, such as a tank, contacts the measuring probe part of the other end side of a vibration rod, the said apparatus suppresses or stops the vibration of a vibration rod, and thereby piezoelectric Since the output voltage from the element changes, it is determined whether or not the charged object is charged up to a predetermined height level according to the magnitude of the output voltage.

By the way, in the above-mentioned conventional apparatus, two places serving as the nodes of the vibration in the vibrating rod are respectively supported by the support, and the vibrations acting on both the supports are 180 °, and the phase difference of the vibrations is 180 °, so if the amplitudes are the same, they cancel each other out. And theoretically zero.

By the way, in order to make the amplitude of both support bodies the same, the circular metal thin film of the same diameter and thickness of the same material is used as both support bodies. However, if both supports are set to a small thickness of the same dimension, since the bearing force against the vibration rod is weak, it becomes difficult to stably support the vibration rod for a long time, and the reliability is lowered. On the other hand, when both supports are set to a large thickness of the same dimension, the support is supported up to a nearby point other than the node of the vibration of the vibration rod, so that both supports serve as a large resistance to the vibration of the vibration rod, thereby attenuating the vibration. In order to obtain vibration of a predetermined amplitude, power consumption in the piezoelectric element is increased.

In addition, since both support bodies are circular of the same diameter, one support body inserts a vibration rod into the slit-shaped attachment hole at the time of manufacture, and fixes it by welding to the predetermined location of a vibration rod, and inserts a vibration rod into this support body. One cylindrical sheath is fixed by welding against one end of an opening, while the other support inserts a vibration rod into its slit attachment hole and welds against the other end opening of the sheath, and is also fixed to the vibration rod by welding. It is assembled in order. In the step of connecting the one support to the end face of one end of the protective tube, the protective tube is welded while holding the protective tube concentrically with the jig. The other support is then welded against the end face of the other end opening of the protection tube while keeping the protection tube concentric with the rod. Thus, the workability of assembly is bad because welding must be carried out while holding a protective tube concentrically with both support bodies which consist of metal thin films.                         

Further, in the conventional apparatus, since the measuring probe portion of the vibration rod is in an environment in which the charged object filled in the tank is blown up, the blown up filler is easily attached to the upper side of the vibrating rod and is deposited. When the vibration of the vibrating rod is suppressed by this, it can be erroneously detected that the to-be-filled object is filled to predetermined height level.

Therefore, an object of the present invention is to provide a vibrating level sensor capable of supporting a vibrating rod stably for a long time while actively suppressing attenuation of vibration by two thin-film supports.

In order to achieve the above object, a level sensor according to one configuration of the present invention is a base and a free end is a rod, the tip is a rod that is placed in the storage container of the object to be charged, and an exciter for adding vibration to the rod ( A supporter of a circular thin film type for supporting the rod at two places where the rod becomes the vibration node, and a cylindrical protective tube covering between the two nodes of the rod, wherein one of the supports is one side of the protective tube. The end of is fitted to the inner surface to be fixed, and the other support has a larger outer diameter than the one of the supports, and is fixed against the other end face of the protective tube. The support close to the place where the exciter on the rod is mounted is set thicker than the other support.

Here, it is preferable that the thicker support of both supports having different thicknesses is positioned closer to the base end of the rod than the other supports.                     

The level sensor is installed in a state in which the base end of the rod is inserted into a storage container such as a tank for filling liquid, powder, or the like, and drives vibration to add vibration to the rod. When the charged object inside the container is filled to a height level in contact with the tip of the vibrating rod, since the vibration of the rod is suppressed by the charged object, the frequency of the excitation electric signal changes, and the charged object is changed by this frequency change. It is detected that it is filled up to a level of a predetermined height.

In this level sensor, since the support near the place where the exciter is mounted on the rod is thicker than other supports, the vibration added from the exciter to the rod has a relatively small amplitude at the center frequency and has a smooth Q value. Therefore, even when the charged object is blown up and attached to the upper surface of the rod, the variation in vibration frequency due to the charged object attached to the upper surface of the rod can be suppressed to a small degree, and thus Misdetection that the object to be charged has been filled to a predetermined height level can be prevented. Moreover, since the bearing force in the vicinity of the place where the exciter in the rod was mounted increases, the rod can be stably supported for a long time, thereby improving the reliability. In addition, since only one support is thick, the restraint of vibration by both supports is not so large that the damping amount of vibration by the support is not so large as a whole, and thus the power consumption of the exciter is not increased.

In this level sensor, both supports have different outer diameters. At the time of assembling the sensor unit, first, the support members of the circular thin film type are attached to two places that are nodes of the rod vibration by fixing means such as welding. Subsequently, when the protective tube is inserted from one support side with a small outer diameter and moved to a position covering both nodes of the rod, the other end face of the protective tube is brought into contact with the other outer peripheral edge of the support having a large outer diameter, and further with one of the protective tubes. The outer circumferential cross section of one support is fitted to the inner circumferential surface of the end portion of the end portion. In this state, the protective tube and both supports are fixed by fixing means such as welding. In this way, both supports of the circular thin film type can be simultaneously positioned and fixed with respect to the rod, and the fixing can be performed irrespective of the protective tube, so that welding or the like for fixing can be performed quickly and easily. In addition, since the cylindrical protective tube can be bonded to both fixed states of the support, it is possible to solve the difficult task of welding while maintaining the protective tube in the conventional sensor concentrically with respect to the rod.

In one embodiment of the present invention, the materials of both supports may be different.

If only one support body located in the front-end side of a rod is formed from a stainless metal thin film, for example, it will be hard to rust even if this support body contacts with a to-be-filled object. If the other support which is not in contact with the to-be-charged material is formed of a metal thin film such as brass of low cost, high reliability can be obtained while suppressing the increase in the material cost of both supports.

A level sensor according to another aspect of the present invention includes a rod having a proximal end and a proximal end, the distal end of which is disposed within a storage container of a to-be-filled object; A circular thin film support supported at two places serving as nodes, and a cylindrical protective tube covering between the nodes of the rod, wherein the rod is made of an elongated flat plate extending horizontally, and the plane of the plate is in a horizontal direction. The slanted surface is set vertically toward the top, and a slanted end is formed upward on the upper side.

According to the above configuration, even if the object to be blown up and attached to the upper side of the rod, the adhered body slips along the slanted end surface and is quickly removed from the upper side of the rod. Therefore, the charged object can be prevented from adhering to the upper side of the rod in a deposited state and thus the vibration frequency of the rod can be prevented. Therefore, there is no erroneous detection that the charged object is filled to a predetermined height level by the attachment of the charged object.

◆ Embodiment

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described in detail, referring drawings.

1 is a longitudinal cross-sectional view showing a level sensor according to a first embodiment of the present invention, and FIG. 2 is a plan sectional view of a main portion thereof.

In these drawings, the cylindrical protective tube 7 is connected to the distal end of the casing 1 by which the main body case portion 2 and the attachment socket portion 3 are screwed together by fixing means such as welding. At both ends of (7), the first and second support bodies 4 and 9 of the circular thin film type are fixedly attached by welding in a state in which the opening of the protective tube 7 is closed in an airtight state. The rod 8 which consists of a flat strip | belt-shaped metal flat plate has the slit-type attachment hole (not shown) formed in the center part of the said support bodies 4 and 9 by setting the plane 8a of the flat plate to the horizontal direction vertically. ) And welded to both supports (4, 9) at two places where the node of vibration appears when the rod (8) is excited through the protective tube (7). , 9). Both supports 4 and 9 are made of a metal thin film, and since the rigidity is low, the rod 8 is elastically supported. The base end side (right end side of the figure) of the rod 8 enters into the attachment socket part 3, and the front end side (left end side of the figure) protrudes from the protective tube 7. The supporting structure of both the supports 4 and 9 of the rod 8 will be described later in detail.

The additional weight body 10 is positioned by the positioning screw 11 and fixed by the fixing screw 12 between the center portion of the protection tube 7 in the rod 8, that is, between the two nodes. In addition, a pair of piezoelectric elements 14A, 14B and an exciter are attached to both surfaces at the base end side of the first support 4 of the rod 8. The piezoelectric elements 14A and 14B are fed through the lead wires 18 from the driving circuit section 17.

As shown in FIG. 3, the drive circuit unit 17 converts the AC power of the general AC power source 17a into a DC power source in the rectifier circuit 17b to feed power to one piezoelectric element 14A. . This piezoelectric element 14A converts the supplied electrical energy into mechanical energy to add vibration to the rod 8. Mechanical energy due to the vibration of the rod 8 is converted into electrical energy by the other piezoelectric element 14B. The output voltage of the piezoelectric element 14B is extracted only the vibration component from the band pass filter 17c of the drive circuit section 17, and the output signal of the band pass filter 17c is amplified by the amplifying circuit 17d and then rectified circuit. Superimposed on the DC power of 17b and input to the relay output circuit 17e. When a predetermined electric signal is input, the relay output circuit 17e turns on an indicator light (not shown) provided in the indicator window lens 19 shown in FIG. 1 and enters into a storage container 20 such as a tank. A power supply stop signal is output to a feeder (not shown) of the thinly charged object 13.                     

The lead wire 18 for connecting the drive circuit portion 17 and the piezoelectric elements 14A, 14B is clamped with the rubber clamp washer 23 by clamping the rubber clamp screw 21 of FIG. 2 to the rubber clamp plate 22. It is pressed and fixed to the inner surface of the attachment socket part 3 by the fixing rubber 24 which is sandwiched between the rubber clamp plates 22 and protrudes laterally. A portion of the lead wire 18 pressed against the attachment socket portion 3 by the fixing rubber 24 is covered and protected by the protection tube 31 shown in FIG. 2. In addition, the casing 1 fastens the female screw portion 2a provided on the tip cylindrical portion of the main body case portion 2 to the male screw portion 3a of the attachment socket portion 3, and further includes a main body case portion ( The front end of 2) is fixed by a lock nut 28 fastened to the male screw portion 3a while the collar portion 3b of the attachment socket portion 3 is pressed through the gasket 27, and the main body is fixed. The case part 2 and the attachment socket part 3 are hermetically connected. The rear end opening of the main body case part 2 is closed by the case cover 30 through the packing 29 shown in FIG.

The level sensor of the above-described configuration is mounted at a position of a predetermined height of the side wall of the storage container 20 in FIG. 1 in a horizontal arrangement. That is, the attachment hole 20a is formed in the site | part corresponding to the position of the height where the to-be-filled object 13 of the side wall of the storage container 20 should be filled, and the socket 32 which has a female thread part in this attachment hole 20a is provided. It is fitted and fixed by welding. The level sensor fastens the tapered screw portion 3c formed on the attachment socket portion 3 of the casing 1 to the female screw portion 32a of the socket 32, and also tightens the collar portion 3b of the attachment socket portion 3. It is airtightly attached to the storage container 20 while pressing the edge part of the attachment socket part 32 via the gasket 33.

4 is a plan view schematically showing a supporting component of the rod 8 in the level sensor. In this figure, the dashed-dotted line shows the oscillation curve when the rod 8 is excited in the primary oscillation mode, and at this time, the two places where the node of the oscillation appear can be displaced by both supports 4 and 9. It elastically supports and excites the rod 8 in the primary vibration mode. Between the nodes of vibration in the rod 8 is a sinusoidal oscillation curve, but in the rod 8 the proximal side and the proximal side with respect to the vibrating bodies 4, 9 become free ends showing a straight vibration curve, and the rod 8 The front end side (left side) of () is arrange | positioned in the state which enters in the storage container 20 of FIG. 1 as a measurement probe part.

In addition, as shown in FIG. 4, although both the support bodies 4 and 9 are formed in the circular thin film, the 1st support body 4 located in the position close to the piezoelectric element 14A, 14B which acts as an excitation group is The thickness D is larger than the thickness d of the second support 9, and the outer diameter R of the second support 9 is larger than the outer diameter r of the first support 4. have. The second support body 9 is welded to the protective tube 7 in contact with an end portion 7a, which is formed concavely in the cross section of its one end opening, while the first support body 4 is welded to the protective tube 7. It is fitted and welded to the inner circumferential surface of the other end opening. Therefore, the protective tube 7 is made to cover between the two nodes of the rod (8). In addition, the first support 4 is formed of a brass thin film, the second support 9 is formed of a stainless thin film. In addition, the protection tube 7 and the attachment socket part 3 are fitted and welded to the edge part provided in the cross section of each other, and are welded.

Next, the operation of the level sensor will be briefly described.

In the piezoelectric element 14A shown in FIG. 3, direct current power is supplied from the rectifying circuit 17b of the drive circuit section 17, and a vibration force is added by the noise component included in the direct current power. The tip end of the inside of the storage container 20 of 2 vibrates in a horizontal direction as shown by the arrow in FIG. As shown in FIG. 1, when the filling surface H of the charge object 13 of the storage container 20 is lower than the rod 8, it is included in the output voltage of the other piezoelectric element 14B. The vibration component is extracted by the band pass filter 17c of FIG. 3, amplified by the amplifier circuit 17d, and superimposed on the direct current power of the rectifier circuit 17b and input to the relay output circuit 17e. The relay output circuit 17e determines that the vibration component included in the input voltage from the piezoelectric element 14B of FIG. 3 is within a predetermined frequency range, and determines that the object to be charged 13 is not charged.

When the filling surface H of the filler object 13 of FIG. 1 rises to a height position in contact with the rod 8, the vibration of the rod 8 is suppressed or stopped by the filler object 13, and the relay output The circuit 17c determines that the vibration component included in the input voltage from the piezoelectric element 14B is out of the predetermined frequency range, turns on the indicator light, and informs the completion of charging. A supply stop signal is output to the feeder to stop the operation of supplying the filled object 13 to the storage container 20.

In the above-described level sensor, since the first support body 4 close to the place where the piezoelectric elements 14A and 14B in the rod 8 are mounted is larger in thickness than the second support body 9, it is loaded from the piezoelectric element 14A. The vibration added to (8) has a relatively small amplitude at the center frequency and has a smooth Q value. Therefore, even when the to-be-filled object 13 blows up and adheres to the upper surface part of the rod 8, since the fluctuation of the vibration frequency by the dust etc. which adhered to the upper surface side of the rod 8 can be suppressed so that it may become small In addition, it can prevent that the to-be-filled object 13 filled to the predetermined height level by the to-be-filled object. In addition, since the bearing force near the place where the piezoelectric elements 14A and 14B are mounted in the rod 8 increases, the rod 8 can be stably supported for a long time, thereby improving reliability. In addition, since only the first support 4 is thick, compared to the case where both supports 4 and 9 are thickened, since the restraint force of vibration by both supports 4 and 9 does not become very large, The attenuation amount of the vibration does not increase too much, and the power consumption of the piezoelectric elements 14A and 14B also does not increase.

Next, the assembly of the level sensor will be described with reference to FIG. 5.

First, as shown to (a), the 2nd support body with a large outer diameter is inserted in this attachment hole, and it positions in the predetermined position of the front end side of the rod 8 which becomes a node of vibration, The rod 8 is fixed to the rod 8 by welding. Subsequently, as shown in (b), after attaching the additional mass 10 to the predetermined position of the rod 8 with the fixing screw 12, the first support 4 is shown in (c). As described above, the rod 8 is inserted into this attachment hole and positioned at a predetermined position on the base end side of the rod 8 which becomes the node of vibration, and then fixed to the rod 8 by welding. As described above, unlike the conventional apparatus for welding while supporting the protective tube, the circular supporters 4 and 9 of the circular thin film type can be fixed regardless of the protective tube 7, so that welding work for fixing can be easily and quickly performed. It can be done. In addition, after positioning both support bodies 4 and 9, the rod 8 can also be welded simultaneously.

Subsequently, as shown by the dashed-dotted line in (d), the protective tube 7 inserts this support body 4 from the side of the 1st support body 4 with small outer diameter, and covers between both nodes of the rod 8. When it moves to a position, the edge part 7a of the front end side cross section of the protective tube 7 in the state which the outer peripheral cross section of the 1st support body 4 was fitted in the inner peripheral surface of the base end opening of the protective tube 7 was fitted. It is attached to the outer peripheral part of the 2nd support body 9 with a large outer diameter. In this state, the protective tube 7 and the two support bodies 4 and 9 are fixed by welding. Here, the protective tube 7 is fitted to the inner circumferential surface of the first support 4 in a fixed state at one end of the proximal end, thereby being supported concentrically with respect to the rod 8, thereby providing Since welding can be easily supported and facilitated, welding of the protective tube 7 to the 1st support body 4 becomes easier. Therefore, it is possible to solve the difficulty in the work of welding while maintaining the protective tube in an unstable state concentrically with the rod when assembling the conventional apparatus.

Subsequently, as shown in (e), after attaching the piezoelectric elements 14A and 14B to both surfaces of the predetermined part of the rod 8, the socket part 3 of the casing 1 is attached to the protective tube 7. Connect by butt welding. The lead wires 18 of the piezoelectric elements 14A and 14B are drawn out to the outside through the attachment socket portion 3, and are inserted into the rubber clamp washers 23 and the fixing rubber 24 to insert the rubber clamp plates 22. The rubber clamp screw 21 temporarily fixed in the gap is interposed between the plurality of lead wires 18 in the opening of the attachment socket portion 3.

Then, as shown in (f), the rubber clamp screw 21 is screwed to the rubber clamp plate 22, and the rubber clamp washer 23 and the rubber clamp plate 22 are sandwiched from both sides to fix the rubber ( 24 is deformed so as to protrude to the side, and each lead wire 18 is pressed to the inner surface of the attachment socket portion 3 to fix it. Thereafter, when the main body case part 2 is connected to the attachment socket part 3 by the above-described screwing and fixed with the lock nut 28, the assembly is completed. In this way, the lead wire 18 can be easily operated by the clamping operation of the rubber clamp screw 21, and at the same time, the rod 8 including the socket portion 3, the support bodies 4 and 9, and the piezoelectric body are provided. The element 14A, 14B, the additional mass 10, and the protective tube 7 can be united as a sensor part, and the main body case 2 side containing the drive circuit part 17 is common, and it unitized to this. Many types of level sensors can be configured by appropriately selecting and attaching various sensor units.

6 to 8 show a level sensor according to a second embodiment of the invention. In these drawings, the same or similar components as those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof will be omitted. In the level sensor, the rod 15 made of an elongated flat plate extending horizontally has its flat surface 15a vertically set also horizontally. The only difference from the first embodiment is that the inclined surfaces 15b and 15c are formed on the upper side of the rod 15, and the upper side is in the shape of a thin and pointed tip toward the upper side. As for the inclination-angle (alpha) with respect to the horizontal of the inclined surfaces 15b and 15c shown in FIG. 8, 20-70 degrees are preferable, More preferably, it is 30-60 degrees. In this embodiment, α = 45 °.

In the above-described level sensor, even when the object to be charged 13 is blown up when it is thrown into the storage container 20, it falls on the upper surface of the rod 15, but the attachment is inclined on both sides of the rod 15 having a thin end shape. It slips off according to (15b, 15c) and is removed promptly. Therefore, since the vibration frequency of the rod 15 can be prevented from being changed, it can be prevented from erroneously detecting that the to-be-filled object 13 is completed by the to-be-filled object which adhered to the upper surface of the rod 15. FIG.

In this level sensor, similarly to the first embodiment, the thickness of the first support body 4 close to the place where the piezoelectric elements 14A and 14B are mounted on the rod 15 is thicker than that of the second support body 9. Since the malfunction due to the deposition of dust on the upper side of the rod 15 can be prevented, contrary to the embodiment, the thickness of the second support 9 is set thicker than that of the first support 4, Even if a vibration having a steep characteristic Q value is added to the rod 15, there is no fear of malfunction. In this case, the state of charge up to the predetermined height level of the object to be filled 13 can be detected with high accuracy according to the change of frequency.

In addition, as shown in FIG. 9, the inclined surfaces 15b and 15c may be formed in the upper side of the rod 15 so that the horizontal surface 15d may remain in the apex part.

There is an effect of providing a vibrating level sensor capable of supporting a vibrating rod stably for a long time while actively suppressing the attenuation amount of vibration by two thin-film supports.

Claims (4)

A rod having a proximal end and a proximal end, wherein the proximal end enters and is disposed in the storage container of the object to be charged; An exciter for adding vibration to the rod; A circular thin film support for supporting the rod at two places, which are nodes of vibration; And A level sensor comprising; a cylindrical protective tube covering between the nodes of the rod, One of the supports is fitted and fixed to the inner surface of one end of the protective tube, the other of the support has a larger diameter than the one of the support, and is fixed against the other end surface of the protective tube, The support body close to the place where the exciter in the rod is mounted is set thicker than the other support body. The method of claim 1, And the support on the thicker side is located closer to the base end of the rod than the other support. The method of claim 1, The level support is characterized in that the support material is different from each other. A rod having a proximal end and a proximal end free of charge, the distal end of which is disposed within the storage container of the object to be filled; An exciter for adding vibration to the rod; A circular thin film support for supporting the rod at two places, which are nodes of vibration; And A level sensor comprising; a cylindrical protective tube covering between the nodes of the rod, The rod is made of a long elongated flat plate extending horizontally, the plane forming the front and back surface of the flat plate is disposed perpendicular to the horizontal direction, the width is narrower toward the top at the vertical upper edge of the flat plate A level sensor, characterized in that the inclined surface is formed.

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