Measuring and testing – Liquid level or depth gauge – Sight glass
Reexamination Certificate
1998-11-23
2003-06-17
Kwok, Helen (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Sight glass
C073S293000, C073S323000
Reexamination Certificate
active
06578418
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to sight glasses providing optical information of the level of a liquid in an enclosed container. More particularly the invention is directed to sight glasses for visually monitoring the level of refrigerant in refrigeration and air-conditioning systems.
BACKGROUND OF THE INVENTION
The identification of the level of refrigerant charge in a refrigeration and air-conditioning system is critical and failure to do so often results in difficulties. Adding too much refrigerant to the system may cause operating inefficiency, system failure, and can lead to broken tubes, fittings, and component failure due to over pressurization. A misdiagnosis of an undercharged system caused by the leaking out of the refrigerant often delays repairs. Liquid indicating sight glasses are used to allow a person to visually monitor the level of the refrigerant in refrigeration and air-conditioning systems. These sight glasses require a light source to be read correctly. The reading must be done in close proximity to the sight glasses in order to determine the presence of refrigerant in the refrigeration and air-conditioning systems.
Liquid indicating sight glasses have historically consisted of flat glasses in gasketed metal fittings that allow the inspection of the interior of a vessel or tube. Refrigeration and air-conditioning sight glasses are manufactured by fusing glass into a steel fitting. A hand-held flashlight or other light emitting device is used to direct light through the glass to identify the presence of clear or slightly translucent fluids in a vessel or tube. The difficulty with these sight glasses is that, while they can clearly identify a partially full condition, where the sight glass is only partially covered, they can be easily misread when completely full or the level of the liquid is below the bottom of the sight glass. This misreading is of particular concern and most indicative of an inexperienced observer or technician.
Alternatives are presently available such as a sight glass that has a propeller inside the sight glass that rotates when there is liquid flow. There are also sight glasses that use a series of horizontal prisms on a front sight glass that distorts the image, such as the word “FULL”, printed on a surface behind the sight glass. When the narrow space between the sight glass and the surface is filled with liquid, the word “FULL” is clearly visible.
R. L. Nagel in U.S. Pat. No. 2,943,530 discloses a liquid level indicator for providing an optical stimuli as a function of electrolyte level in a battery. The level indicator is a post joined to a battery cap. The lower end of the post has a lateral extension and a notch equal to the diameter of the post. The notch is defined by plane angular and longitudinal surfaces. The bottom of post is colored green. The outside lateral surface of the extension colored red is located in lateral alignment with the upper angular surface of the notch. When the notch is full of electrolyte, the color green will be observed by viewing the top of the cap. The color red is observed when the level of the electrolyte is below the upper angular surface of the notch.
SUMMARY OF THE INVENTION
The invention is an apparatus termed a sight glass, for providing visual information concerning the presence of liquid n a structure having a chamber for holding a liquid and the level of liquid in the chamber. The structure is a tube, vessel or a hosing in a fluid line accommodating a liquid, such as a refrigerant. The housing has a chamber for holding the liquid. The presence of liquid and level of liquid in the fluid line is determined by the level of liquid in the chamber. The chamber is enclosed with a cap having a window to allow visual inspection of the chamber and a liquid level indicator located in the chamber. In one embodiment of the liquid level indicator, a convex head on the indicator closes an opening in the cap whereby the liquid level indicator is directly viewed to determine the presence of liquid an the level of liquid in the chamber.
The liquid level indicator has a transparent body of glass, plastic, fused quartz or ceramic materials. The viewing end of the body has a convex lens to enhance illumination of light into the body. The opposite end of the boy has a colored member which provides colored visual information of the presence and level of liquid in the chamber. Prismatic indentations in opposite sides of the body reflect light laterally when exposed to a gas and allow light to pass through the body when exposed to liquid. The light reflects from the colored member back through the body providing colored visual information concerning the presence of liquid in the chamber. The prismatic indentation comprises a pair of longitudinally spaced V-grooves in opposite sides of the body that intersect the longitudinal center line of the body. The V-grooves overlap at their apexes and have a radial depth of about one third the diameter of a cylindrical transparent body. In one embodiment of the liquid level indicator the body has two pairs of V-grooves. Each pair of V-grooves has a groove on opposite sides of the body. The second pair of V-grooves is circumferentially located 90 degrees from the first pair of V-grooves. This liquid level indicator provides visual information concerning full, empty, three quarter, half and one-quarter liquid conditions of the levels in the chamber.
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Frank Rodney
Kwok Helen
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