# Hydraulic Proportional – Spools with Internal Regen

R-spool: Internal hydraulic regeneration – Combines B to P in spool! – Blocked center, so cylinder could creep R3-spool: Internal regen – connects B-to-P path…

# Hydraulic Proportional – Regen Spools with external bypass

W3-spool: hydraulic regeneration extends cylinder quickly. Rod side is blocked by B port. High pressure on rod end pushes flow over external check valve –…

# Hydraulic Proportional – Additional Spool Types

W6-spool: improved W-spool – crossover all ports are closed (to stop) – then decompress at center, open 2% A to T and B to T…

# Hydraulic Proportional – Asymmetrical Spools

Asymmetric spools like E1-, W1-, V1- – 2:1 flow area (4 notches vs. 2 notches) – For differential area cylinders Balances ?p across each flow…

# Hydraulic Proportional – Common Proportional Spools

E-spool: All ports blocked – Overlap 10% to 20% on each side – Differential cylinder may creep, due to leakage in cylinder and spool –…

# Hydraulic Proportional – Power Limits

All direct operated proportional valves have Power Limits ( Qvalve · ?pvalve ) Bernoulli forces try to center spool at high ?pv Power Limit decreases…

# Hydraulic Proportional – Can Valve Pressure Drop Be Too High?

Yes, valve ?p over 50% system pressure is high Avoid over-flowing valve! curve 5 High flow forces try to center spool on direct operated proportional…

# Hydraulic Proportional – Using Flow Diagrams

Estimate ?p required across valve in both flow paths, System pressure – Load pressure Each housing size may have several spool flow options Find a…

# Hydraulic Proportional – Flow Rating of Proportional Valves

Required Flow is normally given, Qreq Nominal valve drop ?p = 10 bar (145 psi) You must estimate pressure drops, To find a spool, solve…

# Hydraulic Proportional – Nominal Flow Rating of Proportionals

“Nominal Flow” for proportional spools is rated at ?p = 10 bar (145 psi) total, 5 bar per land Example 4WRA “Nominal Flow” is 7…