Hydraulic circuit system for hydraulic excavator
US5673558A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1996 |
| Grant date | Oct 7, 1997 |
| Priority date | — |
| Expiry date | Feb 13, 2016 |
Classification
- Technology area (CPC E)Fixed Constructions
- CPC primaryE02F9/2285
- WIPO fieldCivil engineering
- WIPO sectorOther fields
Abstract
For enabling a boom to be smoothly raised during the triple combined operation of boom-up, arm-crowd and bucket-crowd in a hydraulic circuit system for a hydraulic excavator, in a first valve group of a hydraulic valve apparatus (12), a variable throttle valve (70) is installed in a feeder passage (32) of a bucket directional control valve (21) downstream of a load check valve (32a), and a secondary pressure C as a boom-up operation command is introduced through a line (71) to a pilot control sector (70a) of the variable throttle valve (70) which sector operates in the throttling direction, so that when the secondary pressure C is 0 or small, the variable throttle valve (70) is fully opened and, as the secondary pressure C increases, an opening area of the variable throttle valve (70) is reduced to restrict the flow rate of a hydraulic fluid supplied through the bucket directional control valve (21).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.