JPH075379Y2 - Capacitance type level sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial application field" The present invention relates to improvement of a capacitance type level sensor for detecting a level of a liquid surface (referred to as a liquid level) by a capacitance value between electrodes.

"Prior Art" Conventionally, as shown in FIG. 4, in this type of level sensor, a plurality of spacers 3 are interposed between an elongated cylindrical outer electrode 1 and an inner electrode 2 so as to be coaxial with each other. To be done. Smallly centered on axis lines l ₁ , l ₂ and l ₃ that are radially drawn at intervals of 120 degrees from the axis on a plurality of parallel planes that are approximately evenly spaced in the longitudinal direction of internal electrode 2 and that are orthogonal to the central axis. A hole 2a is formed in the peripheral wall of the internal electrode. Their small hole 2a, bosses 3a formed on one end surface of the spacer 3 made of an insulating material such as Teflon is pressed from the outside, each spacer of the internal electrode 2 along the axis l _1, l _2, l ₃ It is mounted radially from the outer peripheral surface.

The insulating cylinder 4 whose one end is closed is attached to the inner peripheral surface of the inner electrode 2 so as to close the opening of one end of the inner electrode 2, and the metal flange 5 is attached to the outer peripheral surface of the one end of the external electrode 1 by coaxial screws. Can be installed at. The insulating disc 6 is screwed onto the closed surface of the insulating tube 4. Internal electrode 2 is press-fitted along the central axis l ₀ from the opening of the flange 5 side of the external electrode 1, the periphery of the insulating disc 6 is secured by screws to the flange 5. One end of a connection cable is attached to each of the electrodes, and the other end thereof is connectable to a capacitance meter, but it is not shown.

The level sensor assembled in this manner is erected vertically in the liquid storage tank, and the wire is passed through the mounting hole 5a of the flange 5 to be connected to the proper position and supported so as not to fall.

"Problems to be solved by the device" The liquid storage tanks installed in general ships and tankers are extremely large, and the size and weight of the level sensor applied to them are large, and the number of parts is large, resulting in an increase in work efficiency during assembly. become worse. When a large vibration or shock is applied to the level sensor for some reason, a large load is applied to the insulating disc 6 and the insulating disc 6 is cracked, so that the relative positions of both electrodes are displaced, and electrostatic discharge between the electrodes is caused. There was a risk that the volume would change and that an error would occur in the measured liquid level.

Also, due to vibration and shock, the liquid rises between both electrodes,
When contacting the inner surface of the insulating disk 6 and then descending, the liquid run-off deteriorated, and it took time for the measured value of the liquid level to return to a steady value, making it difficult to use as a measuring device.

The present invention is intended to solve such a conventional drawback.

"Means for Solving the Problem" A slender cylindrical outer electrode and an inner electrode are coaxially arranged, and a plurality of spacers are mounted between these electrodes at equiangular intervals as viewed from the axial center. In the capacitance type level sensor in which the spacer of is arranged in multiple stages in the longitudinal direction of the electrode, in the present invention, the external electrode and the internal electrode are located at positions intersecting with a straight line orthogonal to their central axes, A pair of through holes are formed in each, common metal connecting rods are inserted into the through holes, and insulating bushes are passed on both sides of the connecting rods, and the diameters of these insulating bushes are sequentially varied in three stages. Two step portions are respectively formed, each outer step portion is in contact with the outer peripheral surface of the external electrode, and each inner step portion is in contact with the outer peripheral surface of the inner electrode. Between both ends of the To have.

[Embodiment] An embodiment of the present invention is shown in FIG. 1 by assigning the same reference numerals to portions corresponding to those in FIG. In this device,
In a specific step (one or more) of the steps to which the spacers 3 of both electrodes are to be attached, the axis l _i (any of l _{1 to} l ₃ ) and the extension line thereof in which the spacer 3 is conventionally arranged are A pair of through holes 1b and 2b are formed in the peripheral wall that intersects with the external electrode 1 and the internal electrode 2, respectively. Through hole 1b in this example
Has an inner diameter slightly larger than that of the through hole 2b. Insulating bushes 7 are inserted into the through holes 1b and 2b from both outer sides of the external electrode 1, respectively. For the insulating bush 7, a material that is not deteriorated by liquid is selected. For example, in the case of liquefied natural gas (-162 ° C.), ethylene trifluoride resin, epoxy glass laminated material or the like is used. Each diameter of the insulating bush 7 is sequentially changed in three stages to form two step portions, respectively, that is, as shown in FIG. 2, the small diameter portion 7a fitted into the through hole 2b and the through hole 1b are fitted. Large diameter part 7b and large diameter part 7b
It is composed of a flange portion 7c having an even larger outer shape.

A metal connecting rod, for example, a bolt 8 made of stainless steel is inserted into the pair of insulating bushes 7, and a nut 9 is screwed to the tip end of the connecting rods so that both ends of the insulating bush are tightened and project from the nut 9. A pin 10 is engaged with a small hole provided at the tip of the bolt 8 to prevent the nut 9 from coming off. Due to the two steps of the insulating bush 7, the distance between both electrodes is kept uniform even if the spacer 3 is omitted.

When the internal electrode 2 is thin and the through hole 2b may become an edge and damage the insulating bush 7, it is desirable to attach the insulating sleeve 11 to the through hole 2b as shown in FIG. That is, when the spacer 3 is attached to the internal electrode 2, the insulating sleeve 11 is fitted into the through hole 2b, and the insulating bush 12 is fitted into the through hole 1b after press-fitting the internal electrode 2 into the external electrode 1. To do. In this case, the insulating bush 12 having no small diameter portion is used.

At the stage of the internal electrode 2 to which the bolt 8 is attached, the spacer 3 may be omitted altogether or may be left partially. The conventional insulating cylinder 4 and insulating disk 6 are omitted. It is desirable that the bolt 8 is grounded via the shielded wire 14 so that external noise is not picked up. Insulating bush 7,
The outer shape of 12 is preferably selected to be equal to or less than that of the spacer 3 or slightly larger than that of the spacer 3 in order to improve the linearity of the liquid level-capacitance characteristic.

[Advantage of Invention] According to this invention, the outer electrode 1 and the inner electrode 2 are integrally connected to each other by a bolt 8 (referred to as a metal connecting rod), so that the relative positions of the two electrodes in the axial direction and the circumferential direction can be improved. It is possible to prevent the displacement of the insulating disc 6, and it is possible to eliminate the conventional fragile insulating disc 6. Also, since the connecting members can be provided at a plurality of positions depending on the magnitude of the load applied to the sensor, both electrodes can be maintained strong and stable against vibration and impact.

Since the liquid does not adhere to the inner surface of the insulating disc 6, the liquid is well drained, and the measured value of the liquid level shows a steady value in a short time, which solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a perspective view of the insulating bush 7 of FIG. 1, and FIG. 3 is a longitudinal sectional view of an essential part showing another embodiment of the present invention. FIG. 4 is a view showing a conventional electrostatic capacity type level sensor, A is a plan view, B is a sectional view taken along line AA of A, and C is a bottom view.

Claims (1)

[Scope of utility model registration request] 1. An elongated cylindrical outer electrode and an inner electrode are arranged coaxially with each other, and a plurality of spacers are mounted between the electrodes at equiangular intervals as viewed from the axis. In the capacitance type level sensor arranged in multiple stages in the longitudinal direction, a pair of through holes are formed in the external electrode and the internal electrode at positions intersecting with a straight line orthogonal to their central axes, A common metal connecting rod is inserted through the through holes, and insulating bushes are inserted on both sides of the connecting rod. These insulating bushes each have a diameter of 3 steps and two step portions are formed. And each outer step is contacted with the outer peripheral surface of the external electrode,
An electrostatic capacitance type level sensor, wherein each inner step is in contact with the outer peripheral surface of the internal electrode, and both ends of the insulating bushes are clamped by the connecting rod.