US3172479A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic power lift mechanism for tractors
Assignee: David Brown Tractors Canada Ltd
•
Filing: 1961-06-22
•
Granted: 1965-03-09
•
Expires: 1981-06-22
Abstract
No abstract record available.
Inventors
- 👤 Ashfield Herbert Edward
- 👤 Hull Charles Hartley
- 👤 Horsfall Harry
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 21:14
CPC Classifications
A; A01; A01B; A01B63/00; A01B63/02; A01B63/10; A01B63/111; A01B63/112
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
154 words
IN APPARATUS FOR COMBINATION WITH A TRACTOR ADAPTED TO HAVE AN IMPLEMENT HITCHED THERETO AND HAVING MECHANISM FOR RAISING AND LOWERING SAID IMPLEMENT BETWEEN IDLE AND WORKING POSITIONS RESPECTIVELY, SAID APPARATUS COMPRISING A POWER DRIVEN PUMP CONNECTED INTO A SUBSTANTIALLY CLOSED HYDRAULIC CIRCUIT, HYDRAULIC MEANS ADAPTED TO BE OPERABLY CONNECTED TO SAID IMPLEMENT RAISING AND LOWERING MECHANISM AND CONNECTED TO BE ACTUATED BY LIQUID PRESSURE AT THE DISCHARGE SIDE OF THE PUMP, A DIFFERENTIAL PRESSURE-RESPONSIVE VALVE IN SAID CIRCUIT FOR CONTROLLING THE ESCAPE OF LIQUID FROM SAID HYDRAULIC MEANS TO SUMP, A SPRING-CLOSED PILOT VALVE FOR CONTROLLING THE PRESSURE DROP ACROSS SAID DIFFERENTIAL PRESSURE-RESPONSIVE VAVE, MEANS FOR CONTROLLING THE FORCE OF THE SPRING OF SAID PILOT VALVE IN RESPONSE TO VARIATIONS IN THE DRAFT FORCE EXERTED BY THE TRACTOR ON AN IMPLEMENT HITCHED THERETO, AND FURTHER VALVE MENAS FOR PREVENTING THE LIQUIE PRESSURE ACTING ON THE HYDRAULIC MEANS FOR FALLING BELOW A PREDETERMINED VALUE.
Claim 2
Dependent Claim
154 words
IN APPARATUS FOR COMBINATION WITH A TRACTOR ADAPTED TO HAVE AN IMPLEMENT HITCHED THERETO AND HAVING MECHANISM FOR RAISING AND LOWERING SAID IMPLEMENT BETWEEN IDLE AND WORKING POSITIONS RESPECTIVELY, SAID APPARATUS COMPRISING A POWER DRIVEN PUMP CONNECTED INTO A SUBSTANTIALLY CLOSED HYDRAULIC CIRCUIT, HYDRAULIC MEANS ADAPTED TO BE OPERABLY CONNECTED TO SAID IMPLEMENT RAISING AND LOWERING MECHANISM AND CONNECTED TO BE ACTUATED BY LIQUID PRESSURE AT THE DISCHARGE SIDE OF THE PUMP, A DIFFERENTIAL PRESSURE-RESPONSIVE VALVE IN SAID CIRCUIT FOR CONTROLLING THE ESCAPE OF LIQUID FROM SAID HYDRAULIC MEANS TO SUMP, A SPRING-CLOSED PILOT VALVE FOR CONTROLLING THE PRESSURE DROP ACROSS SAID DIFFERENTIAL PRESSURE-RESPONSIVE VAVE, MEANS FOR CONTROLLING THE FORCE OF THE SPRING OF SAID PILOT VALVE IN RESPONSE TO VARIATIONS IN THE DRAFT FORCE EXERTED BY THE TRACTOR ON AN IMPLEMENT HITCHED THERETO, AND FURTHER VALVE MENAS FOR PREVENTING THE LIQUIE PRESSURE ACTING ON THE HYDRAULIC MEANS FOR FALLING BELOW A PREDETERMINED VALUE.
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) | 1968-03-08 | 1968-09-07 | 1969-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1972-03-08 | 1972-09-07 | 1973-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1976-03-08 | 1976-09-07 | 1977-03-09 | $7700.00 | Window Closed / Lapsed |