Pressure compensated spool valve
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
Mar 24, 1981
Grant Date -
N/A
app pub date -
Oct 29, 1979
filing date -
Oct 29, 1979
priority date (Note) -
Expired
status (Latency Note)
A preliminary load of PAIR data current through [] has been loaded. Any more recent PAIR data will be loaded within twenty-four hours. |
PAIR data current through []
A preliminary load of cached data will be loaded soon.
Any more recent PAIR data will be loaded within twenty-four hours.
Next PAIR Update Scheduled on [ ] |
Importance
US Family Size
|
Non-US Coverage
|
Patent Longevity
|
Forward Citations
|
Abstract
A control valve for actuating a double acting hydraulic jack or lift cylinder features a pressure compensator assembly for limiting the rate of retraction of the cylinder and piston relative to each other under heavy loading conditions to prevent dropping a load or letting the load get out of control. Pressure compensation is provided by a floating piston which is movably coupled in releasable engagement with a spool, wherein engagement of the piston with the spool defines a restricted flow path for limiting hydraulic flow out of the blind end of the cylinder to tank during retraction. According to a preferred embodiment, the spool is provided with a plurality of notches defining restricted flow passages which are covered and uncovered by the piston as it moves into and out of engagement with the spool. A compression spring is coupled between the piston and the spool for biasing the piston for movement away from the spool. The piston is provided with axially spaced pressure faces whose effective areas are balanced with respect to each other for driving the piston against the spring to a hydraulic detent position in which the notches are exposed. As the valve assembly opens to increase the orifice area of the notches, a pressure drop occurs across the notches, and the piston is held in equilibrium in the detent position as the forces developed by the piston pressure faces and by the spring balance each other. Variations in the cylinder port hydraulic pressure are compensated by the piston to maintain a constant pressure drop across the notches as it moves to choke off or throttle flow through the notches in response to the forces developed by the spring and pressure faces.
First Claim
Family
- 15 United States
- 10 France
- 8 Japan
- 7 China
- 5 Korea
- 2 Other
Patent Owner(s)
- HYDRA RIG INC
International Classification(s)
Inventor(s)
Inventor Name | Address | # of filed Patents | Total Citations |
---|---|---|---|
Elliston, Thomas L | Ft. Worth, TX | 11 | 359 |
Cited Art Landscape
- No Cited Art to Display
Patent Citation Ranking
Forward Cite Landscape
- No Forward Cites to Display
Maintenance Fees
Fee | Large entity fee | small entity fee | micro entity fee | due date |
---|
Fee | Large entity fee | small entity fee | micro entity fee |
---|---|---|---|
Surcharge after expiration - Late payment is unavoidable | $700.00 | $350.00 | $175.00 |
Surcharge after expiration - Late payment is unintentional | $1,640.00 | $820.00 | $410.00 |
Full Text
Legal Events
Matter Detail
Update Public Data Dismiss Edit SaveRenewals Detail
Edit SaveNote
The template below is formatted to ensure compatibility with our system.
Provide tags with | separated like (tags1|tags2).
Maximum length is 128 characters for Customer Application No
Mandatory Fields * - 'MatterType','AppType','Country','Title','SerialNo'.
Acceptable Date Format - 'MM/DD/YYYY'.
Acceptable Filing/App Types -
- Continuation/Divisional
- Original
- Paris Convention
- PCT National
- With Priority
- EP Validation
- Provisional Conversion
- Reissue
- Provisional
- Foreign Extension
Acceptable Status -
- Pending
- Abandoned
- Unfiled
- Expired
- Granted
Acceptable Matter Types -
- Patent
- Utility Model
- Supplemental Protection Certificate
- Design
- Inventor Certificate
- Plant
- Statutory Invention Reg
Advertisement
Advertisement
Advertisement
Recipient Email Address
Recipient Email Address
Comment
Recipient Email Address
Success
E-mail has been sent successfully.
Failure
Some error occured while sending email. Please check e-mail and try again!
PAIR load has been initiated
A preliminary load of cached data will be loaded soon. Current PAIR data will be loaded within twenty four hours.
File History PDF
Thank you for your purchase! The File Wrapper for Patent Number 4257456 will be available within the next 24 hours.
Add to Portfolio(s)
To add this patent to one, or more, of your portfolios, simply click the add button.
This Patent is in these Portfolios:
Add to additional portfolios:
Last Refreshed On:
Changes done successfully
Important Notes on Latency of Status data
Please note there is up to 60 days of latency in this Status indicator for certain status conditions. You can obtain up-to-date Status indicator readings by ordering PAIR for the file.
An application with the status "Published" (which means it is pending) may be recently abandoned, but not yet updated to reflect its abandoned status. However, an application filed less than one year ago is unlikely to be abandoned.
A patent with the status "Granted" may be recently expired, but not yet updated to reflect its expired status. However, it is highly unlikely a patent less than 3.5 years old would be expired.
An application with the status "Abandoned" is almost always current, but there is a small chance it was recently revived and the status not yet updated.
Important Note on Priority Date data
This priority date is an estimated earliest priority date and is purely an estimation. This date should not be taken as legal conclusion. No representations are made as to the accuracy of the date listed. Please consult a legal professional before relying on this date.
We are sorry but your current selection exceeds the maximum number of portfolios (0) for this membership level. Upgrade to our Level for up to -1 portfolios!.