Fluent material handling – with receiver or receiver coacting mea – Evacuation apparatus
Reexamination Certificate
2003-06-27
2004-12-14
Mancene, Gene (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Evacuation apparatus
C141S002000, C141S018000, C141S059000, C141S048000, C141S142000, C184S001500
Reexamination Certificate
active
06830082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of vehicle maintenance, and more specifically, to performing fluid exchanges with vehicular subsystem components having fluid reservoirs such as automatic transmission fluid systems.
2. Description of Related Art
Automatic transmissions and other vehicular fluid system components frequently require servicing such as replacing used fluid with fresh fluid in order to properly maintain them and extend the life of the component and associated vehicle. Early attempts at developing automatic transmission fluid transfer machines often resulted in relatively lengthy and complicated procedures. Many of these devices relied upon compressed gases to circulate the fluid and thus required some sort of compressed air source adding to the device's complexity. Such early attempts also required significant manual operation and supervision as the operator had to continually monitor gauges and other instruments to monitor the fluid flow to achieve the desired performance.
While some of these devices proved satisfactory for their time, the next level of automatic transmission fluid transfer machines introduced a degree of automation to the fluid exchange process thus reducing the extent of operator intervention. However, the plumbing proposed in an effort to automate the process and perform the steps typically associated with a complete automatic transmission fluid service, typically employed a relatively large number of plumbing components such as multiple dedicated pumps, gauges, and several valves. While many of these devices have also proven satisfactory in their performance there remains a push for reducing the number of components, costs associated with manufacture and maintenance, and reducing the overall assembly time while maintaining the capability to perform the desired procedures.
Efforts to resolve this long standing problem led to the introduction of a number of devices of the single pump variety. Some examples of these single pump devices can be found in U.S. Pat. Nos. 5,482,062 and 5,337,708 to Chen; U.S. Pat. No. 5,447,184 to Betancourt; U.S. Pat. No. 5,472,064 to Viken; U.S. Pat. No. 6,035,903 to Few, owned by assignee of this application; and Japanese Unexamined Patent Application No. 2-72299. It is clear from a review of the devices shown in these patents that, while success was achieved in reducing some number of components, such as the pumps, it was necessary to increase the remaining plumbing in order to perform the necessary fluid transfer processes such as complete fluid exchange, recirculation, and draining both used and new fluid tanks or such desired processes could not performed using a single pump. Frequently a separate drain pump or a more complicated and costly reversible pump has been incorporated to perform the desired fluid servicing tasks. While some of these devices, such as that described in U.S. Pat. No. 6,035,903, have proven satisfactory in the field, there remains the ever present need to develop a fluid changing apparatus with a minimal number of components to reduce costs, maintenance, and assembly time, yet still perform the fluid servicing procedures associated with an automatic transmission service.
What is also evident, in addition to a continued focus on improving the plumbing arrangements of these devices, is that a related drive to improve the overall speed of the servicing procedures has shed some light on the deficiencies of some of the automatic control systems. For instance, the primary type of sensor incorporated in automatic fluid transmission exchangers is a pressure sensor for measuring the hydrostatic pressure head created by a column of air atop a column of fluid within a fluid compartment. Such pressure transducers typically incorporate a hollow plastic tube projecting into a fluid containment area, often from beneath the tank creating an increased likelihood of leakage. The open ended tube includes a movable membrane responsive to the pressure head created by the column of air within the tube which changes as the fluid level changes. As the membrane moves, a transducer converts the mechanical movement to an electrical signal indicative of the level of the fluid. To calculate the volume of the fluid, it is necessary to know the geometric configuration of the tank, the fluid density, and an atmospheric pressure reading to give a true pressure reading.
While such devices using such sensors have proven useful and commercially successful, they present several drawbacks. For example, the use of moving mechanical components adds to the likelihood of increasing maintenance costs if the unit fails which is further exacerbated by the below tank installation. Also, the measurements of such pressure transducers are subject to the inaccuracies due to the formation of foam within the fluid as well as a phenomenon known as “wicking” wherein the hydrogen molecules in the fluid actually seep outwardly into the plastic tubing of the fluid tube eventually saturating the tube. Due to this condition, increased maintenance is required as the pressure sensor tubes must be removed on a periodic basis and struck to remove the undesirable fluid buildup and reinstalled. In the meantime, the accuracy of the device may be questionable.
As the accuracy of measuring the fluid in both the used and new fluid tanks is critical to completely drain the old fluid and replace an equal volume of new fluid as well as regulating the flow of fluid into the transmission and out of the transmission to avoid transmission starvation and thereby damaging the transmission, degradation of sensor accuracy is a serious concern. For instance, the accuracy for a typical pressure sensor with such construction measuring the level of fluid in a fluid level tank of an automatic fluid exchanger may have up to a 4-5% margin of error.
As operators request that the speed of the fluid removal continues to be increased so that more fluid exchange servicing procedures can be performed in a day to increase their profit margins, the margin of error introduced by such pressure sensors is not always acceptable given the precision required by more advanced automatic fluid transmission exchangers that are attempting to introduce faster, more powerful pumps to keep up with customer's demands. Sensor accuracy can make all the difference in a commercially successful machine.
Thus, while most devices have an acceptable tolerance level to accommodate routine servicing, there remains a need for alternative methods of measuring the fluid level that overcome the drawbacks of the hydrostatic pressure head sensors as well as increase the overall accuracy of the fluid level measurement in the fluid tanks. Such an improvement provides more accurate control of the fluid exchange process providing a more stable exchange, reducing fluid waste, and decreasing the likelihood of a dry transmission run. Accurate measurements also improve the topping off procedure at the end of the fluid exchange process.
What is needed and heretofore unavailable is an improved sensor feedback system based on alternative principles with increased accuracy to support high flow fluid changing machines while providing a modular construction for reducing installation time and maintenance costs.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus for performing fluid exchange servicing functions for a vehicle having a fluid reservoir is described herein and more particularly for servicing the transmission and power steering components of a vehicle system. Such fluid servicing apparatus generally includes new and used fluid tanks, each with a respective sensing unit, at least one of which may sense a change in capacitance corresponding to a fluid level within the tank to generate a fluid level signal transmittable to a processing unit for use in commanding selective operation of a fluid flow rate control device interposed between the reservoir and the tanks to direct and control the rate of fluid flow therebetwe
deVore Peter
Fulwider Patton Lee & Utecht, LLP.
Mancene Gene
Norco Industries Inc.
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