Temperature sensitive dipstick

Abstract

A fluid level indicator for determining the level of fluid in a container includes a dipstick that is entered into the fluid in the container and withdrawn from the fluid, a billet of thermochromic material having a reference temperature, a billet length extending along a portion of the dipstick, and a fluid level range marking on the dipstick along the length of the billet.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates generally to determining the level of fluid in a container. More particularly the invention pertains to sensing the temperature of the fluid.[0003]2. Description of the Prior Art[0004]Accurately measuring transmission oil or engine crankcase oil level in a repeatable manner has been challenging because, when the dipstick is pulled out of a fill tube, the oil level is not clearly indicated. An oil film left on the dipstick does not provide a clearly visible demarcation. In addition, the dipstick can contact the side of the fill tube causing oil film to be formed in areas above where the actual oil level is located. This results in a measurement system that does not provide a repeatable, reliable indication of the oil level in the vehicle.[0005]Additionally, transmission oil should be warmed to be about 150° F. before reading the oil level. Often the vehicle operator or service technician has no eas...

AI Technical Summary

Benefits of technology

[0007]The fluid level indicator employs a heat sensitive material, preferably thermochromic plastic, which changes color at a reference temperature, sometimes called a transition temperature. Thermochromic plastics are available in many different colors, which fade to white above the transition temperature or become transparent above the transition temperature. The fluid level indicator provides a visible indication of the level of fluid in a container that is accurate, repeatable, and easy to use.

[0008]A billet, secured to an end of a dipstick, is made of multiple lengths of thermochromic plastic materials, each material selected to transition in color at the reference temperature. A thermal insulator, located between each length, minimizes conductive heat transfer among the lengths along the billet's length.

[0009]The billet can then be secured to the indicator end of any dipstick. The middle two sections of the billet's length can represent the mid-range of fluid level specified by the vehicle manufacturer and the outermost sections indicate underfill and overfill fluid levels, respectively. A larger number of billet sections provide increased precision of the indicated fluid level.

[0010]The thermochromic plastic indicator provides the user a clear and certain indication of both the oil level and that the fluid has been heated to the proper temperature compatible with the manufacturer's recommendation for reading the oil level.

Problems solved by technology

Accurately measuring transmission oil or engine crankcase oil level in a repeatable manner has been challenging because, when the dipstick is pulled out of a fill tube, the oil level is not clearly indicated.

An oil film left on the dipstick does not provide a clearly visible demarcation.

This results in a measurement system that does not provide a repeatable, reliable indication of the oil level in the vehicle.

Often the vehicle operator or service technician has no easy technique way to determine transmission oil temperature without the use of a diagnostic tool.

Transmission oil level is very important in automatic transmission function since too much oil may reduce fuel economy and can result in venting fluid.

Too little oil degrades function under cold conditions.

These constraints often lead to a very tight oil level tolerance (about 0.5 liters), which may be difficult to verify using conventional dipsticks.

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