Patent US3777899A successfully refreshed from Google Patents.
US3777899A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bounce-preventing control for hydraulic cylinder
Assignee: HARRISCHFEGER CORP
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Filing: 1972-08-14
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Granted: 1973-12-11
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Expires: 1992-08-14
Abstract
Abstract A crane boom is raised and lowered by the extendable and retractable cylinder rod of a hydraulic boom hoist cylinder. A main pump supplies pressurized operating fluid to the cylinder through a lever controlled manually operable three-position (raise, lower, neutral) main control valve. A pilot valve operating holding valve on the cylinder maintains the rod in extended position. To prevent bounce and fluctuation as the cylinder rod is retracted and the boom is lowered, the pilot valve is supplied with pilot fluid from a fluid source other than the cylinder or main pump and is operated by the same lever that operates the main control valve.
Inventors
- 👤 W Witwer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 01:01
CPC Classifications
F; F15; F15B; F15B11/00; F15B11/16; F15B11/20; B; B66; B66C; B66C23/00; B66C23/62; B66C23/64; B66C23/70; B66C23/701; B66C23/705
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
187 words
In a machine having a component movable in opposite directions by at least one extendible and retractable hydraulic cylinder, a main control valve having extend, neutral and retract positions for operating said cylinder, a releasable holding valve being open and closed positions to maintain said cylinder in extended position, a pilot pressure control valve for operating said holding valve, said valves each having an axially movable valve spool, independent sources of hydraulic operating fluid including separate pumps for said main control valve and for said pilot pressure control valve, and operating means comprising a manually operable lever and a control rod movable by said lever for operating said main control valve and said pilot pressure control valve, said control rod being connected to move the valve spool of said main control valve, and said operating means also comprising a connecting linkage between said control rod and the valve spool of said pilot pressure control valve, said operating means effecting operation of said pilot pressure control valve to cause opening of said holding valve when said operating means effects operation of said main control valve to retract position.
Claim 2
Dependent Claim
187 words
In a machine having a component movable in opposite directions by at least one extendible and retractable hydraulic cylinder, a main control valve having extend, neutral and retract positions for operating said cylinder, a releasable holding valve being open and closed positions to maintain said cylinder in extended position, a pilot pressure control valve for operating said holding valve, said valves each having an axially movable valve spool, independent sources of hydraulic operating fluid including separate pumps for said main control valve and for said pilot pressure control valve, and operating means comprising a manually operable lever and a control rod movable by said lever for operating said main control valve and said pilot pressure control valve, said control rod being connected to move the valve spool of said main control valve, and said operating means also comprising a connecting linkage between said control rod and the valve spool of said pilot pressure control valve, said operating means effecting operation of said pilot pressure control valve to cause opening of said holding valve when said operating means effects operation of said main control valve to retract position.
Claim 3
Dependent Claim
209 words
In a mobile crane having a boom, at least one extendible and retractable hydraulic boom hoist cylinder for raising and lowering said boom, a first pump for supplying pressurized fluid to operate said cylinders, a main control valve connected between said first pump and said cylinder to operate the latter, said main control valve having boom-hoist, neutral, and boom-lower positions, a holding valve on said cylinder and having a closed position to maintain said boom extended and having an open position to allow retraction of said boom, a second pump, a pilot pressure control valve connected between said second pump and said holding valve to operate the latter, said pilot pressure control valve having a closed position wherein it maintains said holding valve in closed position and having an open position wherein it maintains said holding valve in open position, and operating means for said main control valve and said pilot pressure control valve, said operating means effecting closure of said pilot pressure control valve when said main control valve is in neutral position; effecting opening of said pilot pressure control valve when said main control valve is in boom-lower position; and effecting closure of said pilot pressure control valve when said main control valve is in boom-hoist position.
Claim 4
Dependent Claim
209 words
In a mobile crane having a boom, at least one extendible and retractable hydraulic boom hoist cylinder for raising and lowering said boom, a first pump for supplying pressurized fluid to operate said cylinders, a main control valve connected between said first pump and said cylinder to operate the latter, said main control valve having boom-hoist, neutral, and boom-lower positions, a holding valve on said cylinder and having a closed position to maintain said boom extended and having an open position to allow retraction of said boom, a second pump, a pilot pressure control valve connected between said second pump and said holding valve to operate the latter, said pilot pressure control valve having a closed position wherein it maintains said holding valve in closed position and having an open position wherein it maintains said holding valve in open position, and operating means for said main control valve and said pilot pressure control valve, said operating means effecting closure of said pilot pressure control valve when said main control valve is in neutral position; effecting opening of said pilot pressure control valve when said main control valve is in boom-lower position; and effecting closure of said pilot pressure control valve when said main control valve is in boom-hoist position.
Claim 5
Dependent Claim
64 words
A crane according to claim 2 wherein said main control valve and said pilot pressure control valves both have axially movable valve spools and wherein said operating means comprises: a manually operable control lever, a control rod connected to said main control valve spool and movable by said lever, and a connecting linkage between said control rod and said pilot pressure control valve spool.
Claim 6
Dependent Claim
73 words
A crane according to claim 3 wherein said connecting linkage comprises: a first member affixed to and movable with said control rod, a second member connected to said pilot pressure control valve spool and spaced from said first member, a compression spring disposed between said first and second members, and means connected between said first and second members to limit separation of said members while allowing said members to move toward each other.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-12-10 | 1977-06-11 | 1977-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-12-10 | 1981-06-11 | 1981-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-12-10 | 1985-06-11 | 1985-12-11 | $7700.00 | Window Closed / Lapsed |