US3654833A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic control circuit
Assignee: Eaton Corp
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Filing: 1970-06-29
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Granted: 1972-04-11
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Expires: 1990-06-29
Abstract
Abstract A hydraulic control circuit for raising or lowering a load includes a hydraulic ram having a movable load engaging piston therein and a pressure compensated hydraulic pump for supplying fluid thereto for raising a load. Means are provided in the circuit between the pump and the hydraulic ram for controlling the raising and lowering operations of the ram. Further means are provided for locking the position of the load in the event of mechanical or hydraulic failure of any portion of the load raising mechanism.
Inventors
- 👤 Thomas C Griffiths
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:24
CPC Classifications
F; F15; F15B; F15B11/00; F15B11/003; F15B2211/00; F15B2211/20; F15B2211/205; F15B2211/20507; F15B2211/20515; F15B2211/30; F15B2211/305; F15B2211/30505; F15B2211/30525; F15B2211/31; F15B2211/3105; F15B2211/3116; F15B2211/3144; F15B2211/315; F15B2211/31523; F15B2211/31529; F15B2211/32; F15B2211/327; F15B2211/40; F15B2211/405; F15B2211/40515; F15B2211/45; F15B2211/50; F15B2211/505; F15B2211/50509; F15B2211/50518; F15B2211/80; F15B2211/86; F15B2211/8609
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
271 words
A hydraulic control circuit for operating a hydraulic ram comprising: a source of hydraulic fluid; a pump operatively conNected to the source of fluid for drawing fluid therefrom; a hydraulic ram including a piston and rod adapted to be extensibly and retractably driven by pressurized fluid from the pump; a control valve operatively associated with the output of the pump for selectively controlling fluid flow from the pump to the hydraulic ram and from the ram to the source of fluid; a first flow restricting means for generating a back pressure in the fluid between the hydraulic ram and the source of fluid in response to operation of said pump; a first pilot operated check valve disposed to normally prevent flow from the rod end of said ram to said source, the pilot of said first check valve being operated to open said first check valve in response to a pretermined fluid pressure between said pump and the blind end of said ram; a second check valve disposed to normally prevent flow from the rod end of said ram to said source; a second flow restricting means disposed in parallel with said second check valve to regulate flow from the rod end of said ram to said source; and a third pilot operated check valve disposed to normally prevent flow from the rod end of said ram to said source, the pilot of said third check valve being operated to open said third check valve in response to a pretermined back pressure being generated by said first flow restricting means which is located between said ram and said source of fluid.
Claim 2
Dependent Claim
271 words
A hydraulic control circuit for operating a hydraulic ram comprising: a source of hydraulic fluid; a pump operatively conNected to the source of fluid for drawing fluid therefrom; a hydraulic ram including a piston and rod adapted to be extensibly and retractably driven by pressurized fluid from the pump; a control valve operatively associated with the output of the pump for selectively controlling fluid flow from the pump to the hydraulic ram and from the ram to the source of fluid; a first flow restricting means for generating a back pressure in the fluid between the hydraulic ram and the source of fluid in response to operation of said pump; a first pilot operated check valve disposed to normally prevent flow from the rod end of said ram to said source, the pilot of said first check valve being operated to open said first check valve in response to a pretermined fluid pressure between said pump and the blind end of said ram; a second check valve disposed to normally prevent flow from the rod end of said ram to said source; a second flow restricting means disposed in parallel with said second check valve to regulate flow from the rod end of said ram to said source; and a third pilot operated check valve disposed to normally prevent flow from the rod end of said ram to said source, the pilot of said third check valve being operated to open said third check valve in response to a pretermined back pressure being generated by said first flow restricting means which is located between said ram and said source of fluid.
Claim 3
Dependent Claim
62 words
The hydraulic control circuit as defined in claim 1 wherein a connecting means extends between an exhaust line from the rod end of the hydraulic ram and the blind end of the hydraulic ram during extension of the hydraulic ram, whereby fluid from the rod end may be mixed with pump pressurized fluid for supply to the blind end of said ram.
Claim 4
Dependent Claim
36 words
The hydraulic control circuit defined in claim 2 further comprising a locking cylinder operatively associated with the hydraulic ram for preventing movement thereof upon loss of hydraulic pressure at the rod end of the hydraulic ram.
Claim 5
Dependent Claim
46 words
The hydraulic control circuit defined in claim 3 further comprising a pressure actuated control valve connected to the exhaust line from the rod end of the hydraulic ram for normally supplying pump pressure to the locking cylinder to prevent locking operation thereof on the hydraulic ram.
Claim 6
Dependent Claim
61 words
The hydraulic control circuit defined in claim 4 further comprising resilient means biasing the pressure actuated control valve toward a position relieving hydraulic pressure in the locking cylinder and permitting operation of the locking cylinder upon the hydraulic ram to prevent movement thereof upon a loss of hydraulic pressure in the exhaust line from the rod end of the hydraulic ram.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-04-11 | 1975-10-11 | 1976-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-04-11 | 1979-10-11 | 1980-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-04-11 | 1983-10-11 | 1984-04-11 | $7700.00 | Window Closed / Lapsed |