Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-07-10
2001-07-10
Lefkowitz, Edward (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S619000, C250S577000
Reexamination Certificate
active
06259370
ABSTRACT:
This application claims the priorities of Japanese Patent Application No. 11-252080 filed on Aug. 3, 1999 and Japanese Patent Application No. 11-376592 filed on Dec. 13, 1999, which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a leak sensor; and, in particular, to a leak sensor which optically detects whether or not a leaked liquid has occurred in a region subjected to leak detection.
BACKGROUND ART
In various facilities such as factories, leaked liquid way cause disasters or damage the facilities themselves, whereby it is necessary to detect the occurrence of leaked liquid at its early stage.
To this aim, there have conventionally been proposed various kinds of optical means which can detect whether leaked liquid have occurred or not. For example, a leak sensor using a filter made of thin paper or the like has been proposed.
This leak sensor emits light to the filter and detects the change in quantity of transmitted light or reflected light in the case where the filter is impregnated with a liquid, thereby determining whether a leaked liquid has occurred or not.
When a highly viscous liquid is subjected t o detection, however, the liquid is hard to infiltrate into the filter, thus making it difficult for the leak sensor using the filter to accurately grasp the change in light quantity, whereby leaked liquid is very hard to detect.
Also, since the filter has to be replaced upon every resetting operation, operators may suffer unexpected disasters upon replacing the filter when a highly dangerous liquid is subjected to detection, unless much attention is paid. Due to inconveniences as such, this kind of leak sensor has not been suitable for practical use.
Therefore, leak sensors using a light-transmitting part constituted by a transparent or semitransparent material in place of the filter made of thin paper or the like have been proposed.
In these leak sensors, for example, a casing is constructed by a transparent or semitransparent glass material, synthetic resin, or the like, while the bottom part thereof or the like is provided with the above-mentioned light-transmitting part.
For example, such a leak sensor utilizes the fact that, when probe light is incident from a medium having a refractive index n1 onto a medium having a refractive index n2 (n1>n2 ), the reflectivity of probe light remarkably changes near its angle of reflection.
Namely, when no leaked liquid occurs, the difference in refractive index between the casing and the light-transmitting part is so large that the probe light having propagated through the casing is mostly reflected by the light-transmitting part and then propagates as reflected light.
If a leaked liquid adheres to the light-transmitting part, on the other hand, then the difference in refractive index between the casing and the light-transmitting part becomes smaller, so that the reflectivity at the boundary between the casing and the light-transmitting part lowers, whereby part of the probe light spills into the leaked liquid, by which the quantity of propagating reflected light decreases.
When a leak sensor employing the light-transmitting part as such is used, whether a leaked liquid has occurred or not can be detected while avoiding the shortcomings of the leak sensor using the filter.
Meanwhile, there are cases where the occurrence of a leaked liquid cannot be detected favorably if a casing is installed as it is in a subject of leak detection.
Namely, while the leak sensor cannot detect a leaked liquid unless it reaches substantially the center part thereof, i.e., a location under the light-transmitting part, if the casing is installed as it is in the subject of leak detection, then the light-transmitting part may attach to the region subjected to leak detection without substantially forming a space therebetween, thus making it hard for the leaked liquid to reach the location under the light-transmitting part.
Also, even when the leak sensor is held so as to form a space from the subjected of leak detection, if the manner of holding is unfavorable, e.g., in a state where the leak sensor is installed such that the light-transmitting part is inclined with respect to the subject of leak detection or the leak sensor is shaky, then the leaked liquid cannot be detected stably.
On the other hand, if the leak sensor is held with a large contact area or too much force so as not to become shaky, the leaked liquid cannot be detected accurately, because of the fact that the light-transmitting part is hidden, distortions and the like occur, and so forth.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a leak sensor which improves the shortcomings of the above-mentioned optical sensor and can accurately detect leaked liquid.
For achieving the above-mentioned object, the present invention provides a leak sensor including a light-transmitting part constituted by a transparent or semitransparent material, the leak sensor irradiating the light-transmitting part with probe light in a state where the light-transmitting part is provided so as to face into a region subjected to leak detection, and detecting a leaked liquid according to a change in quantity of light reflected by a boundary between the light-transmitting part and the region subjected to leak detection;
the leak sensor further comprising attachment means for installing the leak sensor in the region subjected to leak detection, the attachment means comprising a ground portion and a mounting portion.
Here, the ground portion is grounded on the region subjected to leak detection.
The mounting portion rises from the ground portion, and is adapted to mount the leak sensor in a state where the light-transmitting part is parallel to the ground portion and in a state where a predetermined space is formed therebetween.
Preferably, in the present invention, a surface of the ground portion opposing the light-transmitting part is subjected to a surface treatment for reducing a surface tension of the leaked liquid on the ground portion.
Preferably, the present invention further comprises a conduit portion formed in the ground portion so as to guide the leaked liquid to substantially a center part between the light-transmitting part and the ground portion.
Preferably, the present invention further comprises an electric system, an optical system, a casing, and a connection line, the optical system being provided in the casing and installed within the region subjected to leak detection, the electric system being installed at a place separated from the region subjected to leak detection, the optical system and the electric system being connected to each other by the connection line.
Here, the electric system generates probe light for irradiating the light-transmitting part, photoelectrically converts the light reflected by the boundary between the light-transmitting part and the region subjected to leak detection, and detects the leaked liquid according to a change in an output thereof.
The optical system includes the light-transmitting part, irradiates the light-transmitting part with the probe light from the electric system, and collects the light reflected from the light-transmitting part.
The casing is provided with the optical system such that the light-transmitting part is directed to the region subjected to leak detection, while not being provided with the electric system.
The connection line connects the optical system provided in the casing and the electric system to each other, guides the probe light obtained by the electric system to the optical system, and guides to the electric system the reflected light from the light-transmitting part obtained by the optical system.
Preferably, the connection line is an optical fiber comprising an entrance-side fiber and an exit-side fiber.
Here, the entrance-side fiber guides the probe light from the electric system and has an irradiating portion for emitting the light toward the light-transmitting part.
The exit-side fiber has a l
Lefkowitz Edward
Snider Ronald R.
Snider & Associates
Technical & Try Co., Ltd.
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