Abstract: A hydraulic circuit for lifting and lowering a load is disclosed. The hydraulic circuit may include a hydraulic pump, a fluid reservoir, a load-sense valve, and a hydraulic actuator having a first chamber and a second chamber. The hydraulic circuit may also include a first control valve assembly having first and second lowering positions, the valve being disposed between the hydraulic pump and the hydraulic actuator. A second control valve assembly may also be provided that is disposed between the first control valve assembly and the first chamber of the hydraulic actuator. In one embodiment, the second control valve assembly has a first position and a second position. In one embodiment, the load can be selectively lowered by the hydraulic circuit without use of the hydraulic pump when the first control valve assembly is in the first lowering position and the second control valve assembly is in the second position.

Abstract: Hydraulic valve arrangements may be assembled to provide pre-compensation or post-compensation using the same chassis body. A first type of main spool is disposed in a main passage and a first type of pressure compensator spool is disposed in a compensator passage to provide pressure pre-compensation. The first type of pressure compensator spool connects to a first pilot location and not to a second pilot location. A second type of main spool is disposed in the main passage and a second type of pressure compensator spool is disposed in the compensator passage to provide pressure post-compensation. The second type of pressure compensator spool connects to the second pilot location and not to the first pilot location. The valve arrangement may be switched from pre-compensation to post-compensation (or vice versa) by switching out the main spool and pressure compensator spool without making any other changes to the chassis body.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.

Abstract: A hydraulic circuit for lifting and lowering a load is disclosed. The hydraulic circuit may include a hydraulic pump, a fluid reservoir, a load-sense valve, and a hydraulic actuator having a first chamber and a second chamber. The hydraulic circuit may also include a first control valve assembly having first and second lowering positions, the valve being disposed between the hydraulic pump and the hydraulic actuator. A second control valve assembly may also be provided that is disposed between the first control valve assembly and the first chamber of the hydraulic actuator. In one embodiment, the second control valve assembly has a first position and a second position. In one embodiment, the load can be selectively lowered by the hydraulic circuit without use of the hydraulic pump when the first control valve assembly is in the first lowering position and the second control valve assembly is in the second position.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.