Modular load-sensing valves control flow and pressure, permitting simpler, more-versatile hydraulics.
A typical application for M4 valves is on a truckmounted loading crane. A single, variabledisplacement pump supplies the six-section valve that controls various crane functions:
- Main arm
- Articulated arm
- Telescopic cylinder
- Open gripper
- Close/lower gripper
- Slewing gear.
A key requirement is that these functions operate simultaneously, yet with precise control.
The valves must handle changing loads and flows even though hydraulic demands vary, depending on materials being handled and the nature of movement. In such applications, variable-displacement pumps hold an advantage over their fixed-displacement counterparts. Fixeddisplacement pumps always deliver the same flow, regardless of demand. So if the crane sits idle, all the flow dumps to the tank in an inefficient waste of energy. Variabledisplacement, loadsensing pumps, however, only provide the flow required by operations at the valve. The pumps destroke to low-pressure standby until one or more functions engage. This improves system efficiency. For safety reasons, static controls that stabilize the truck typically rely on a different set of valves.
Bosch Rexroth, (330) 263-3434, boschrexroth-us.com