Claims
- 1. A vehicle hydraulic system comprising:
- hydraulic brake means;
- at least two other hydraulic means which, in operation, reduce the availability of hydraulic pressure to said brake means;
- a hydraulic fluid source for providing a supply of hydraulic fluid; and,
- flow control means for controlling fluid flow from said source to said at least two other hydraulic means and including valve means responsive solely to the pressure of said hyraulic fluid immediately upstream of said valve for blocking flow communication with at least one of said at least two other hydraulic means when said pressure upstream of said valve falls below a selected level so as to thereby prevent further reduction of said hydraulic pressure due to said at least one of said at least two other hydraulic means, and including means for blocking flow to said at least two other hydraulic means one after another in sequence of priority in response to continued decreases in the level of said pressure of said hydraulic fluid upstream of said valve.
- 2. A vehicle hydraulic system as set forth in claim 1 wherein said valve includes at least one valve assembly comprising:
- a valve body having a bore formed therein and including a first port for providing flow communications between said bore and said hydraulic fluid source, and at least one further port for providing flow communication between said bore and a corresponding said other hydraulic means;
- a valve spool movably mounted in said bore and structured to either permit or prevent flow of hydraulic fluid from said first port to said at least one further port through said bore in dependence upon the position of said spool in said bore; and,
- means for positioning said spool within said bore in dependence upon the pressure of said hydraulic fluid upstream of said valve.
- 3. A vehicle hydraulic system as set forth in claim 2 wherein said means for positioning said valve spool in said bore includes means defining a pressure chamber adjacent said spool for applying said pressure upstream of said valve across said spool to urge movement of said spool toward a first position wherein flow of hydraulic fluid from said first port to said at least one further port is freely permitted, and loading means for resiliently opposing the movement of said spool toward said first position and for urging movement of said spool toward a second position wherein flow of hydraulic fluid from said first port to said at least one further port is blocked.
- 4. A vehicle hydraulic system as set forth in claim 3 wherein said loading means comprises at least one substantially zero rate compression spring whereby said valve spool moves with a snap action for at least a portion of the distance from said first position to said second position upon said pressure upstream of said valve falling below said selected level.
- 5. A vehicle hydraulic system as set forth in claim 3 wherein said valve spool is further structured to permit flow communication from said first port to at least one but not all of said further ports upon said valve spool be positioned intermediate said first and second positions.
- 6. A vehicle hydraulic system as set forth in claim 5 wherein said valve spool is further structured to sequentially block flow communication from said first port to said further ports in sequence of priority as said spool is moved from said first position to said second position.
Priority Claims (1)
Number |
Date |
Country |
Kind |
25891/73 |
May 1973 |
UK |
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Parent Case Info
This is a division, of application Ser. No. 475,119 filed May 31, 1974, now U.S. Pat. No. 4,014,360.
US Referenced Citations (3)
Foreign Referenced Citations (1)
Number |
Date |
Country |
558,700 |
Mar 1957 |
IT |
Divisions (1)
|
Number |
Date |
Country |
Parent |
475119 |
May 1974 |
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