JP2003344139A - Liquid level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive sensor excellent in the productivity with a simple constitution, which can perform the detection without any problem even when the length of the sensor is long, when a liquid flows, or when a vibration exists in a liquid container, and which can quickly cope with the change in the specifications. <P>SOLUTION: In the liquid level sensor (S) in which, at one end of a coaxial cable (1) made by disposing an inner conductor and an outer conductor through the inner conductor and by coating the outer periphery of the outer conductor with an insulator layer, a pair of electrodes are formed by coating with a conductive resin the end of the inner conductor exposed at an interval in the longitudinal direction of the cable and the end of the outer conductor, and in which a flange with a mounting position fixing sleeve is provided, a member (3) for reinforcing and/or adjusting the flange mounting position is inserted on the outer insulator layer between the flange (2) and the electrode parts (1a and 1b). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level sensor for detecting the liquid level of a liquid having conductivity, and particularly to a liquid level suitable for detecting the liquid level of liquids such as water and chemicals. It relates to a sensor.

[0002]

2. Description of the Related Art Conventionally, an electrode type liquid level sensor (hereinafter sometimes simply referred to as "sensor") for detecting a liquid level of a conductive liquid has a single-core or multi-core cable having two or more cores. Is used. An example of the former is JP 2001-9
No. 9693, and the latter example (coaxial cable) is disclosed in JP-A-7-325056 or JP-A-1-325056.
It is disclosed in Japanese Patent Publication No. 1-304565. Further, in the electrode type liquid level sensor using the coaxial cable, which detects the liquid level of the photosensitive material processing liquid, in order to reinforce the detection part,
It is also known to extend a sleeve below the flange attached to the sensor, that is, a sleeve located at the electrode portion, to the vicinity of the electrode portion. (Japanese Patent Laid-Open No. 2000-257
However, since the flange and the sleeve are integrated in this sensor, if the liquid level position to be detected is different or the specification is changed when changing the liquid level position,
Since it is necessary to prepare a flange provided with sleeves of various lengths corresponding to the respective liquid surface positions, there is a problem that the degree of freedom in design is insufficient. There is also a problem that productivity is poor because it takes time and cost to prepare such a flange. Further, when the liquid tank to be detected is deep, the sensor length inevitably becomes long, so that the tip end portion (electrode portion side) of the sensor held in the liquid tank in the vertical direction is easily shaken. Especially when liquid is flowing or the liquid tank in which the sensor is installed is vibrating, the tip of the sensor may shake or resonate, resulting in an unstable state and sometimes damage. To do. Further, even if the sensor is not damaged, the sensor often bends (warp phenomenon) in the liquid tank, and the position of the electrode portion is deflected accordingly. This deflection not only causes the liquid level detection position to wrap around, but depending on the deflection direction, the electrode part contacts the inner wall of the liquid tank, and at that time, water droplets or water bubbles generated on the wall cause the sensor Malfunction is triggered. As a result, the problem that the liquid surface level cannot be accurately detected appears more significantly, and some sort of reinforcement / vibration and bending countermeasures are indispensable.

[0003]

Therefore, an object of the present invention is to solve the above-mentioned problems when the sensor length is long, when the liquid is flowing, and when the liquid tank vibrates. It is an object of the present invention to provide an inexpensive sensor which has a simple structure and is excellent in productivity, which can quickly respond to a change in sensor specifications with a flange having the same standard.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have proposed a sensor for reinforcing a sensor and / or adjusting a flange mounting position on an outer insulating layer between a sensor flange and a sleeve flange for fixing the mounting position of a liquid level sensor. By inserting the above-mentioned member, the conventional problems can be easily solved.

Thus, according to the present invention, a part of the electric wire member in the cable including the electric wire member and the insulating layer surrounding the electric wire member is exposed, and the exposed portion is provided with an electrode portion coated with a conductive resin. Then, in a liquid level sensor in which a flange provided with a sleeve is attached to an upper portion and a lower portion of the liquid level sensor at a desired position away from the electrode portion, in the outer periphery of the insulating layer between the sleeve below the flange and the electrode portion, There is provided a liquid level sensor, characterized in that a member separate from the sleeve is inserted for reinforcing the sensor and / or adjusting a flange mounting position on the sensor.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to the drawings for an example of a sensor using a two-core type coaxial cable and applying a tube member as an insertion member. FIG. 1 is a front view showing an example of the liquid level sensor of the present invention. FIG. 2 is a front view showing a preferred embodiment of the liquid surface sensor of the present invention. 1 and 2, (S) is a liquid level sensor, (1) is a coaxial cable, and the cable itself has a known structure. That is, the inner conductor,
A coaxial cable comprising an inner insulating layer for insulating the inner conductor, an outer conductor surrounding the inner insulating layer, and an outer insulating layer for insulating the outer conductor. And, at one end of this coaxial cable (1)
As disclosed in JP-A-2579 and JP-A-11-304565, the tip of the inner conductor is spaced from the inner insulating layer, and at the same time, the tip of the outer conductor is spaced from the outer insulating layer in the longitudinal direction of the cable. The pair of electrode portions (1a) and electrode portions (1b) are formed by exposing the exposed portions and further covering the exposed portions with a conductive resin. Further, (2) is a flange for fixing the mounting position of the sensor in the liquid tank, (2a) and (2b) are sleeves integrally attached to the upper and lower parts of the flange (2), respectively (3) Is a tube member that is inserted into the outer periphery of the outer insulating layer between the sleeve (2b) and the electrode portion (1a) and is separate from the sleeve (2b). The tube member (3) reinforces the sensor main body between the sleeve (2b) and the electrode portion (1a), and also, depending on the length thereof, a flange mounting position on the sensor (S), and thus a liquid tank. Function to adjust the mounting position of the sensor at. A feature of the present invention is that the outer insulating layer of the coaxial cable is provided between the sleeve (2b) attached to the lower portion of the flange (2) for fixing the mounting position of the sensor (S) and the electrode portion (1a). A member for reinforcing the sensor itself and / or adjusting a flange mounting position on the sensor is inserted on the outer periphery as a separate body from the sleeve (2b). By doing so, the space between the electrode portion (1a) and the lower end portion of the sleeve (2b) is reinforced in strength. Therefore, even if the sensor length is long, its tip does not shake, and even if the liquid is flowing in the liquid tank or the liquid tank in which the sensor is attached vibrates, the tip of the sensor will not move. It does not shake or resonate, maintains a stable immersion state, and also reduces the risk of breakage, so that the liquid level can be accurately detected. At the same time, since the tube (3) can position the flange (2) based on its length, it also plays a role of adjusting a mounting position of the flange (2) to the sensor. Therefore, even if the specifications such as the detection position of the liquid surface are different, it is possible to deal with it by simply preparing the tubes (3) of various lengths without changing the specifications of the flange itself. The degree of freedom is dramatically improved. The length and thickness of the tube (3) to be inserted are usually 2 for the former in consideration of sensor specifications and reinforcement strength.
0 mm to 1000 mm, 0.5 mm to 2 for the latter
It is appropriately selected from the range of mm. Also tubes (3)
The inner diameter of the coaxial cable may be slightly larger than the outer diameter of the coaxial cable in consideration of ease of insertion work. As a material of such a tube (3), of course, a resin having both heat resistance and chemical resistance is adopted, and among them, a fluororesin is preferably used. Specific examples of the fluororesin include tetrafluoroethylene-ethylene copolymer (E
TFE), polytetrafluoroethylene resin (PTF)
E), tetrafluoroethylene / perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP) and the like. In addition, it is apt to be considered that the above-mentioned tube is more effective in reinforcement and shaking prevention when it is inserted up to the most distal end of the sensor except the electrode part. However, in practice, the distance between the electrodes (between 1a and 1b) is shorter than the distance from the lower part of the flange to the electrodes, and therefore, the influence on the reinforcement and shaking is small. Of course, the distance between electrodes (between 1a and 1b) may be reinforced if necessary. In this case, apply non-conductive resin between the electrode parts before forming the electrodes.
It may be covered or a tube may be inserted. As another aspect, it is conceivable to insert the tube up to the tip of the sensor in advance and then expose only the electrode part. However, this method involves peeling processing of the tube, which makes post-processing complicated. I have a hate. The conductive resin coating the electrode portion is not particularly limited as long as it is a material applied to the coaxial cable. Generally, as the resin, polyvinyl chloride, polyethylene, polyamide or imide, polyester, and the above-mentioned fluorine-based resin, and as the conductive agent, carbon black-based, silver, copper, nickel and the like can be mentioned. The conductivity of the conductive resin itself may be 10 Ωcm or less in terms of volume resistivity.
In the present invention, the above-mentioned reinforcing effect can be further enhanced. For this purpose, the upper end of the tube (3) and the lower end of the sleeve (2b) are brought into contact with each other, and their contact points (P)
It is preferable that both are heat-sealed together. In this case, if the tube (3) and the sleeve (2b) are made of the same material, the heat fusion becomes more reliable. Furthermore, the heat fusion part
It is desirable to cover the entire circumference rather than a part of the circumference.
Next, a preferred embodiment of the liquid level sensor of the present invention will be described based on FIG. In this aspect, the electrode portion (1a), that is, the sleeve (2
A stopper (4) for restricting the insertion position of the tube (3) is provided on the electrode portion closer to b). The presence of such a stopper (4) reliably regulates the insertion position of the tube (3), which facilitates the insertion work and, at the same time, easily determines the attachment position of the flange to the sensor.
In order to provide the stopper (4), a separate stopper (4) may be inserted, or resin or the like may be coated. However, it is simple that a little conductive resin coating the electrode portion (1a) is used. It is to raise the excitement. Next, a mode of fixing the flange (2) to the sensor will be described. First, a tube (3) having a length matched to a predetermined detection position is inserted from the end of the liquid level sensor composed of the coaxial cable (1) on the side opposite to the electrode side to the vicinity of the electrode part (1a). . Next, the flange (2) with the sleeves (2a) and (2b) is inserted, and both are heated at the contact point (P) between the upper end of the tube (3) and the lower end of the sleeve (2b). Fuse together. Finally, the upper end of the sleeve (2a) and the outer insulating layer in contact with the upper end are heat-sealed to each other, so that the flange (2) is
A liquid level sensor in which is firmly fixed in place is completed.
At this time, if the respective ends of the sleeves (2a) and (2b) are tapered, a stronger heat-sealing effect can be obtained. The present invention has been described above using the coaxial cable. On the other hand, when the present invention is applied to a single-core type cable, the reinforcing effect of the sensor is further enhanced. That is, in the single-core type cable, since the electrode portion is formed at one end, the reinforcing tube can be inserted from the other end of the cable to the position just before the electrode portion. Also, the tube which is a tubular body has been described as an example of a member separate from the sleeve for reinforcing the sensor and / or adjusting the flange mounting position on the sensor, but a function comparable to this tube is described. However, there is still a possibility that the resin material may be obtained by means such as extrusion coating or coating.

A specific example of the liquid level sensor of the present invention will be shown below in the case of FIG. ETFE as an internal insulation layer around a tin-plated annealed copper wire (inner conductor) with a wire diameter of 0.6 mm
A resin is coated with a thickness of 0.3 mm, and then a tin-plated annealed copper wire having a wire diameter of 1.4 mm is formed around the inner insulating layer to form an outer conductor having a braided structure, and further, an outer conductor is formed around the outer conductor. ETFE resin as a resin insulator is coated with a thickness of 0.2 mm, the outer diameter is 1.8 mm, and the length is 500 mm.
I prepared a coaxial cable. At one end of this cable, the tip of the inner conductor is exposed from the inner insulating layer, and the tip of the outer conductor is exposed from the outer insulating layer with an interval of 18 mm (exposure length: both 10 mm). A part having a pair of electrode parts (1a) and (1b) was prepared by coating the part with a conductive ETFE resin which is a conductive resin. Next, a tube (3) made of ETFE having a length of 70 mm, an inner diameter of 2 mm, and a thickness (thickness) of 1.0 mm is firstly provided from the end opposite to the electrode parts (1a) and (1b) of the sensor. Then, the inner diameter is 2 mm, the outer diameter is 4 mm, and the length is 19
mm attached with sleeves (2a) and (2b), ET
The flange (2) made of FE was inserted. In this state,
A contact point (P) between the tube (3) and the sleeve (2b),
The joint surface between the upper end of the sleeve (2a) and the outer insulator of the coaxial cable was heat-sealed to fix the flange position at a predetermined position (position 130 mm from the electrode part (1b)). The outer diameter of the flange (2) was 26 mm. Finally, after the end portions of the sensor opposite to the electrode portions (1a) and (1b) of the sensor were processed, a liquid level sensor of the present invention was obtained by attaching a connecting connector. The liquid level sensor thus obtained was attached to a water tank in which tap water is constantly flowing, and the operation status of the sensor was checked. As a result, no operational problem occurred, and the effectiveness of the liquid level sensor of the present invention Was confirmed.

[0008]

According to the present invention, a tube or the like, which is separate from the flange, is inserted into the sensor body between the sleeve below the flange and the electrode portion, that is, the outer periphery of the outer insulating layer, and preferably contact with the flange. Since the points are heat-sealed and fixed, the strength of the tip of the sensor is remarkably improved. As a result, there is no concern about the vibration or resonance of the sensor body and the deflection of the electrode portion even in a liquid with flow or vibration, and accurate detection of the liquid level can be realized. Furthermore, by preparing tubes of various lengths in advance, it is possible to easily respond to changes in the flange mounting position, and the flange mounting structure is simple, so that the cost of the product can be reduced. Not only that, the workability is greatly improved, so the productivity is further improved.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a liquid level sensor of the present invention.

FIG. 2 is a front view showing a preferred embodiment of the liquid surface sensor of the present invention.

[Explanation of symbols]

S Liquid level sensor P Connection point between the lower end of the sleeve attached to the lower part of the flange and the upper end of the tube 1 Coaxial cables 1a, 1b Electrode part 2 Flange with sleeve 2a Sleeve 2b attached to the upper part of the flange 2 Sleeve attached to the lower part of the flange 3 Tube 4 stopper

Claims (7)

[Claims] 1. A cable including an electric wire member and an insulating layer surrounding the electric wire member, wherein a part of the electric wire member is exposed and an exposed portion is provided with an electrode portion coated with a conductive resin, and
In a liquid level sensor having a flange provided with a sleeve on its upper and lower portions at a desired position away from the electrode portion, a liquid level sensor is provided, on the outer periphery of an insulating layer between the sleeve below the flange and the electrode portion, A liquid level sensor, wherein a member separate from the sleeve is inserted for reinforcement and / or adjustment of a flange mounting position on the sensor. 2. The liquid level sensor according to claim 1, wherein the member is a tube member. 3. The liquid level sensor according to claim 2, wherein the lower end of the sleeve below the flange and the upper end of the tube member are heat-sealed in contact with each other. 4. The liquid level sensor according to claim 2, wherein the electrode portion is provided with a stopper that regulates an insertion position of the tube member. 5. The liquid level sensor according to claim 1, wherein both the flange with sleeve and the member are made of fluororesin. 6. The liquid level sensor according to claim 1, wherein an end portion of the sleeve is tapered. 7. The liquid level sensor according to claim 1, wherein the cable is a single core or a multi-core type having two or more cores.