Hydraulic circuit for a boom cylinder in a hydraulic shovel
US5855159A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 18, 1997 |
| Grant date | Jan 5, 1999 |
| Priority date | — |
| Expiry date | Feb 18, 2017 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE02F9/2292
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
A hydraulic circuit for a boom cylinder in a hydraulic shovel has a pressurized discharge fluid from a hydraulic pump that is driven by an engine, the pressurized discharge fluid supplied via a directional control valve for a boom into a retraction pressure chamber and an extension pressure chamber of a boom cylinder for swinging the boom upwards and downwards. A relief valve is included in a circuit for connecting the retraction pressure chamber of the boom cylinder to the boom directional control valve, the relief valve having a relief set pressure. A switching device is included for switching the relief set pressure to a low pressure as well as to a high pressure if the directional control valve is set at a position that is other than a neutral position thereof, when the engine is driven, the switching device being adapted to switch the relief set pressure to a high pressure when the engine is halted.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.