Fluid-pressure and analogous brake systems – Automatic
Reexamination Certificate
1999-07-30
2001-07-24
Swann, J. J. (Department: 3611)
Fluid-pressure and analogous brake systems
Automatic
C137S467000, C137S511000
Reexamination Certificate
active
06264290
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to valve assemblies used in braking circuits, and more particularly, to a single operation valve assembly for an anti-lock braking system circuit.
BACKGROUND OF THE INVENTION
A conventional anti-lock brake system (“ABS”) monitors the wheels of a vehicle and institutes corrective action when the wheels begin to slip or lock up during braking. When the ABS recognizes that one or more of the wheels are slipping during braking, the system reduces the brake fluid pressure applied to the wheel brake of the slipping wheel. Once the wheel begins turning again, the fluid pressure applied to the wheel brake is gradually reapplied until the wheels begin slipping again. Fluid pressure applied to a given wheel brake can be reduced by providing a fluid pressure relief path to an accumulator. Fluid can then be pumped from the accumulator back into the main ABS braking circuit.
It is important in any braking system circuit to assure that air or other gases are not present in the circuit, as the compressible nature of air inhibits proper braking performance. Accordingly, in conventional braking systems a vacuum is drawn on the braking system circuit to remove all gases before brake fluid is introduced into the braking circuit. In some manufacturing environments it is desirable to prefill portions of the braking circuit with brake fluid prior to connecting such pre-filled portions with remaining portions of the overall braking system circuit. When the final braking circuit is constructed having a pre-filled portion and a non-prefilled portion, it is necessary to draw a vacuum on the non-prefilled portion in order to removes gas from the entire braking system circuit. It is also necessary to include one or more valves which prevent the inflow of brake fluid from the prefilled portion when the vacuum is drawn on the non-prefilled portion. Traditional check valves or coffin valves have been used for such purposes in the past. However, such traditional valves present certain problems including remaining in the braking system circuit continuously and having at least some affect in the braking system circuit even after the valve is no longer needed.
SUMMARY OF THE INVENTION
The present invention is a single-operation valve assembly useful in such braking system applications as well as others, enabling prefill of portions of braking system circuits and subsequent drawing of vacuum of other braking system portions. The single-operation valve acts as a fluid “fuse” in that once the flow blocking valve is “blown” the valve thereafter permits fluid flow in either direction. In one embodiment the single-operation valve assembly includes a flow passage and a valve member located within the flow passage at a first position in which the valve member prevents fluid flow from an upstream side of the valve member to a downstream side of the valve member. The valve member and flow passage are configured for movement of the valve member from the first position along the flow passage to a second position along the flow passage when a pressure difference between the upstream side of the valve member and the downstream side of the valve member exceeds a threshold level. The valve member and the flow passage are also configured for free flow of fluid along the flow passage in either direction when the valve member moves to the second position. Thus, in a braking system circuit the subject valve assembly does not interfere with fluid flow in the circuit after the valve member has been blown to the second position.
In another aspect of the invention a method of temporarily blocking flow of a brake fluid along a fluid path of an ABS braking circuit in at least a first direction along the fluid path to enable prefill of a portion of the braking circuit involves providing a flow passage which defines at least a portion of the fluid path and providing a valve member within the flow passage at a first position in which the valve member prevents fluid flow at least from an upstream side of the valve member to a downstream side of the valve member as long a pressure difference between the upstream side of the valve member and the downstream side of the valve member is below a threshold level. A fluid pressure at the upstream side of the valve member is increased until the pressure differential reaches the threshold level and the valve member is moved from the first position to a second position along the flow passage when the pressure reaches the threshold level. The valve member and the flow passage are configured for free flow of fluid along the flow passage in either direction when the valve member moves to the second position.
REFERENCES:
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patent: 3224455 (1965-12-01), Alfieri
patent: 3766940 (1973-10-01), Mason
patent: 3776258 (1973-12-01), Dockins
patent: 3800979 (1974-04-01), Piffath
patent: 4365643 (1982-12-01), Masclet
patent: 4833946 (1989-05-01), Lemieux
patent: 5086613 (1992-02-01), Fox
patent: 5275196 (1994-01-01), Mitchell
patent: 5538336 (1996-07-01), Reuter
patent: 5927832 (1999-07-01), Fulks
patent: 5944068 (1999-08-01), Hool
Bond James Randolph
Borgemenke Daniel Norbert
Derr Randall L.
Fulks Gary Chris
Delphi Technologies Inc.
Divine David
Sigler Robert M.
Swann J. J.
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