The CINDY family of cartridge valves from Bucher Hydraulics, Klettgau, Germany, has been proven for decades in countless industrial and mobile applications. That, according to company officials, is due to features such as extremely low leakage, finger-tip controllability and load-independent cylinder travel behavior.
Bucher Hydraulics has now expanded its well-established CINDY technology offerings with the new size 40 load-control valve. The proportional cartridge-type seat valve offers flow rates up to 1,200 l/min and operating pressures up to 350 bar.
In launching a size 40 version, the company expands the capabilities of the CINDY modular system, which is now available for flow rates from 20 to 1,200 l/min. Important features of this high-performance load-control cartridge valve are its low pressure drop at high flow rates, leak-tightness, and excellent functional stability in systems that are susceptible to oscillation. These are today’s essential criteria for precision control and delicate movement of heavy loads.
Load-control valves in the CINDY series perform functions like preventing hydraulic actuators from running ahead of the incoming oil flow in an uncontrolled manner. Load-holding, safety and pipe-rupture functions are also incorporated in these valves. What’s more, these leak-free load-control valves are well-suited for use at high pressures, where they have a safety factor of at least 3. With various optional functions, the entire CINDY modular system can be extended and adapted to user-specified system requirements.
To expand on details of the valve’s functional operations, company engineers explained that in the inoperative position, the load pressure and the compression spring act on the control spool in the closing direction. The load-control valve is closed with virtually no leakage.
For lifting (flow direction A to B) pump pressure at port A opens the load-control valve against the ‘light’ compression spring and the load. The pilot spool and control spool move together in the opening direction. Oil flows from A to B and the load-control valve then functions as a check valve.
For lowering, (flow direction B to A) pilot pressure at port X acts on the pilot piston and against the control springs. The pilot spool opens and, as a result, load pressure at port B is discharged to port A via the metering grooves in the pilot spool. The progressive characteristic of the decompression phase ensures that the lowering motion begins smoothly and without jerks. If the pilot pressure at port X is increased, the pilot spool opens further. The change in pressure conditions at the control spool means that it follows the pilot spool in the opening direction. Oil flows from B to A.
Features of the valve include high opening pilot ratio (113:1); guaranteed closing force on the control assembly—such as in the case of a broken spring, for example; standard pilot pressures from 6 to 20 bar; and several available damping variants. All exposed parts are zinc-nickel plated for corrosion resistance.
The advantages, according to Bucher officials, include minimum pilot-pressure differential with different loads and highly reliable closing. Also, lowering takes place with minimum energy expenditure, and the valve can be configured for various pressure conditions with different orifice combinations.
Reported benefits for OEMs include improved energy efficiency, thanks to reduced pilot pressure, the elimination of the need for additional safety valves, the possibility of using smaller actuators, and no additional units are required for matching with actuators.
Benefits for the end user include load-independent cylinder travel for the machine operator; increased safety for people and equipment, even when equipment malfunctions; cost savings that result from improved energy efficiency; and finger-tip operation due to a fine-control range.
Typical applications for the premium-grade valves are mobile-, harbor- and ship-cranes, fire-fighting turntable ladders, drilling rigs, underground and tunnel boring machines, aerial work platforms and hydraulic presses.