1、CHAPTER 8DIRECTIONAL VALVESThree-Position ValveThree Position Valve with Transition Condition Fi gur e 8-1 G r aphi c sym bol for 3-posi ti on di r ecti onal val veCOPYRIGHT(2001)EATON CORPORATIONCNo FlowFree FlowBasicCheck ValveFi gur e 8-2 A check val ve i s a one-w ay val ve.Bal l type i s show n
2、COPYRIGHT(2001)EATON CORPORATIONCBall TypeFree FlowNo FlowPoppet TypeFigure 8-3 In-line poppet type check valve operationCOPYRIGHT(2001)EATON COPRORATIONCRight Angle CheckFigure 8-4 Typical right angle check valveCOPYRIGHT(2001)EATON CORPORATIONCRight Angle CheckWith OrificeFigure 8-5 Restriction ch
3、eck valve operationCOPYRIGHT(2001)EATON CORPORATIONCPilot-Operated CheckFigure 8.6 Pilot-to-open check valveCOPYRIGHT(2001)EATON CORPORATIONCPOCheck ValveSmall poppetunseals firstThen largerpoppet opensFigure 8-7 Operation of pilot-operated check valve with decompression poppetCOPYRIGHT(2001)EATON C
4、ORPORATIONCPilotPilotDrainDrainFree FlowBlocked FlowFigure 8-8 Pilot-to-close check valve operationCOPYRIGHT(2001)EATON COPRORATIONCPilot pressure holds valveclosed while pump is runningWhen the pump stops,the valve opens,dischargingthe accumulator to tankFigure 8-9 Automatic accumulator discharge c
5、ircuitCOPYRIGHT(2001)EATON CORPORATIONCAABBTTPPTTABPTFigure 8-10 Two position,three-way spool valveCOPYRIGHT(2001)EATON CORPORATIONCAAABBBTTPPPTTTFigure 8-11 Two-position,four-way spool type valveCOPYRIGHT(2001)EATON CORPORATIONCPABTSpring OffsetAPBTFigure 8-12 Four-way,two position valveCOPYRIGHT(2
6、001)EATON CORPORATIONCPABTAPBTSpring Centered ValveFigure 8-13 Spring-centered valve is a three-position valveCOPYRIGHT(2001)EATON CORPORATIONCPABTSpring OffsetAPBTFigure 8-14 Two-position,four-way valve is spring offsetCOPYRIGHT(2001)EATON CORPORATIONCPABTFigure 8-15 Three-position,four-way detente
7、d valveCOPYRIGHT(2001)EATON CORPORATIONCAPBTFloatCenterClosedCenterOpenCenterTandemCenterPPPPAAAABBBBTTTTAPBTAPBTAPBTAPBTFigure 8-16 Four-way valve center conditionCOPYRIGHT(2001)EATON CORPORATIONCPABTAPBTFigure 8-17 Manually(lever)actuated,three position,four-way valve with spring centeringCOPYRIGH
8、T(2001)EATON CORPORATIONCAPBTPABTCamFigure 8-18 Mechanically actuated(cam roller)four-way valveCOPYRIGHT(2001)EATON CORPORATIONCPABTPilotAir InPilotAir OutAPBTFigure 8-19 Pneumatically actuated four-way valveCOPYRIGHT(2001)EATON COPRORATIONCPABTPilotOil InPilotOil OutFigure 8-20 Hydraulically actuat
9、ed,pilot-operated valveCOPYRIGHT(2001)EATON CORPORATIONCAPBTAMPSA/CPABTArmatureCoilPush PinFigure 8-21 Push-type solenoids commonly used to shift spools of small valvesCOPYRIGHT(2001)EATON CORPORATIONCPABTAMPSA/CFigure 8-22 Armature is pulled into electromagnetic force of the solenoid,shifting the v
10、alve spoolCOPYRIGHT(2001)EATON COPRORATIONCManual OverrideArmaturePush PinDynamic Seal O-RingCoilFigure 8-23 Air gap solenoid designCOPYRIGHT(2001)EATON COPRORATIONCNNSSCore TubeArmatureManual OverridePush PinFigure 8-24 Wet armature solenoid designCOPYRIGHT(2001)EATON COPRORATIONCTimeIn-rush Curren
11、tHolding CurrentFigure 8-25 In-rush and holding current of energized coilCOPYRIGHT(2001)EATON COPRORATIONCCurrentPTABXYPilot StageMain StageExternal Pilot PressureExternal DrainFigure 8-26 Typical solenoid controlled,pilot operated valve(two-stage valve)COPYRIGHT(2001)EATON CORPORATIONCAAPPBBTTyXX75
12、 psi75 psiExternal pilotpressure via theX portInternal pilotpressure via internalpassageways in the valve bodyFigure 8-27 Left:External pilot check valve Right:Return line pilot pressure check valveCOPYRIGHT(2001)EATON COPRORATIONCPTABY PORTDrain Plug PlacementFigure 8-28 Plug options for internal/e
13、xternal drain for pilot valveCOPYRIGHT(2001)EATON CORPORATIONCPTABXYPilot Pressure/Load Drop Check ValveFigure 8-29 Integral pilot pressure check valveCOPYRIGHT(2001)EATON COPRORATIONCAPBTyXAPBTAPxBTyAPBTABXXExternal OperationInternal OperationAPxBTyABFigure 8-30 Variations of two-stage valve symbol
14、sCOPYRIGHT(2001)EATON COPRORATIONCPTABP PORTX PORTPilot Plug PlacementsFigure 8-31 Plug options for pilot pressure supplyCOPYRIGHT(2001)EATON CORPORATIONCPTABXYPilot chokes slow downthe main stage spool shifting speed,reducing system shockAdjustable flow controlsFigure 8-32 Pilot choke mounted on va
15、lveCOPYRIGHT(2001)EATON CORPORATIONCPTABXYSmall volume pin speeds the spool shiftFigure 8-33 Pilot piston speeds spool shiftingCOPYRIGHT(2001)EATON COPRORATIONCPTABXYAdjustable flow controlsStroke LimitersFigure 8-34 Stroke limiter optionCOPYRIGHT(2001)EATON CORPORATIONCD03/NG 6D05/NG10D07/NG16D08/N
16、G 25TPABTPABTTAPBXYTAPBYXD010/NG 32TAPBYXFigure 8-35 Pattern interface terminology for mounting standardsCOPYRIGHT(2001)EATON CORPORATIONCPilot to closePilot to openFrom systemgateFrom tankMain ramProx SensorFigure 8-36 High flow position of a pre-fill valveCOPYRIGHT(2001)EATON CORPORATIONCPilot to closePilot to openFrom systemgateFrom tankMain ramProx SensorFigure 8-37 High pressure position of a pre-fill valveCOPYRIGHT(2001)EATON COPRORATIONCInlet 1Inlet 1Inlet 2Inlet 2OutletOutletFloating BallFigure 8-38 Shuttle valve and symbolCOPYRIGHT(2001)EATON CORPORATIONC
