Pilot valves for two-stage hydraulic devices
US4785839A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 13, 1987 |
| Grant date | Nov 22, 1988 |
| Priority date | — |
| Expiry date | Aug 13, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T137/87217
- WIPO fieldMechanical elements
- WIPO sectorMechanical engineering
Abstract
A pilot valve for a two-stage hydraulic device, the pilot wave comprising a spool slidably mounted in a housing for movement in opposite directions from a normal null position in order to deliver fluid under pressure from an inlet port through one or other of two service ports to a second stage of the device to actuate the latter in one direction or an opposite direction from a normal null position, and an electrically-actuated spool control device, associated with one end of the spool. The pilot valve spool is movable beyond its normal operating range to an offset zero flow position in the event of a failure of a control device. A spring is disposed at one end of the pilot valve spool and is operable, in the event of failure of a control device, to move the spool to a predetermined position. A stop for the spring prevents further movement of the spool beyond the predetermined position. The pilot valve is constructed to allow pressure fluid to react on the pilot valve spool so that when the spring engages the stop, this reaction results in movement of the spool to move the spool fully to the dump position in which both service ports are connected to tank, flow of fluid under pressu…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.