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3 c. industrial pneumatic circuit logic

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Dr.R. SELVAM
Dr.R. SELVAM

This document discusses various pneumatic logic circuits that can be created using spool valves. It describes logic AND, OR, NOT, memory/latch circuits and how they function. Diagrams are provided to illustrate 3/2 valves that can be used for normally open, normally closed, selection, and diversion applications. Circuits for OR, AND, NOT logic functions and single pulse creation are also depicted.

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INDUSTRIAL PNEUMATIC CIRCUIT
3 c. industrial pneumatic circuit logic
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 X Y Z 12 10
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 12 10 X Y Z 12 10
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 X Y Z 12 10 12 10
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 12 10 X Y Z 12 10
Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
Logic AND ? This method must not be used as a two handed safetycontrol ? It is tooeasy toabuse. e.g. one of the buttonscould be permanently fixed down and the system operated from the other buttononly ? Use the purposedesigned two handed safetycontrol unit 2 3 1 12 10 2 3 1 12 10 X Y Z
Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
Logic MEMORY ? A logic MEMORYallows the output signal state (ON or OFF) to be maintained after the input signal has been removed ? Any bi-stablevalve is a logic MEMORY ? With this leverdetented valve, once the lever has been moved X directionorYdirection it can be released and will stay in thatposition Z X 3 1 10 Y 12
Logic MEMORY ? A logic MEMORY allows the output signal state (ON or OFF) to be maintained after thesignal thatset it has been removed Z X 3 1 12 10 Y
Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 10 12 2 1 3 12 10
Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 12 10 2 1 3 12 10
Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 12 10 2 1 3 12 10
Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 2 1 3 12 10 12 10
Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 2 1 3 12 10 12 10
3 c. industrial pneumatic circuit logic
Logic circuits (spool valves) ? 5/2 OR ? Single pulse control ? Air conservation ? Double flow ? Counting ? NO / NC ? Selection / Diversion ? Latch ? OR, AND, NOT ? Single pulse maker ? Slow pressure build ? Pre-select
3/2 NO / NC ? A fully balanced valveallows pressureon any potor combinationof ports ? A singlevalvecan be used normallyopen or normally closed ? For normallyopen thesupply pressure is connected toport 1 ? For normallyclosed the supply pressure is connected toport 3 2 3 1 12 10 2 3 1 12 10
3/2 NO / NC ? A fully balanced valveallows pressureon any potor combinationof ports ? A singlevalvecan be used normallyopen or normally closed ? For normallyopen thesupply pressure is connected toport 1 ? For normallyclosed the supply pressure is connected toport 3 2 3 1 12 10 2 3 1 12 10
3/2 Valve selection / diversion ? Selection of one of two supplies connected toports 1 and 3 can be different pressures ? Diversionof one supply toone of twooutlets ? If it is required toexhaust the downstreamaira 5/2 valve is required 2 3 1 12 10 2 3 1 12 10
3/2 Valve selection / diversion ? Selection of one of two supplies connected toports 1 and 3 can be different pressures ? Diversionof one supply toone of twooutlets ? If it is required toexhaust the downstreamaira 5/2 valve is required 2 3 1 2 3 1 12 10 12 10
Latch with controls ? In thisversionof a latch the push buttonvalves are connected toperform ¡®OR¡¯ and ¡®NOT¡¯ functions ? The ¡®OFF¡¯ valve must be placed last in the signal chain so that if bothvalvesare operated togetherthe ¡®OFF¡¯ command will dominateover the ¡®ON¡¯ command 2 3 1 12 10 2 3 1 10 2 3 1 10 ON 12 OFF 12 Out
OR, AND, NOT ? A single 3/2 pilot operated spring returnvalvecan be use foranyof these logic functions ? x OR y gives output z ? x AND y gives output z ? x gives NOT z 3 1 12 10 12 10 12 10 AND OR NOT x y z 2 x 3 1 y z 2 3 1 x z 2
Single pulse maker ? Convertsa prolonged signal x intoa single pulse z ? Signal z must be removed to allow thevalve to reset then x can beapplied again ? Thedurationof the pulsecan be adjusted with the flow regulator 2 3 1 12 10 x z
Slow initial pressure build up ? Choosea 3/2 pilotspring valve with a relatively high operating forcee.g. 3 to 4 bar ? When the quick connect coupling is made, theoutput at port 2 is controlled at the rateof the f low regulator setting ? When the pressure is high enough tooperate thevalve full flow will takeover 2 3 1 12 10
Pre-select ? The lever valve can pre-select the movement of the cylinder OUT or IN ? The movement will occur the next time the plunger valve is operated ? The plungervalvecan be released immediatelyand subsequently operated and released any numberof times 2 3 1 12 10 2 3 1 12 10 2 3 1 12 10 OUT/IN pre-select
5/2 OR function ? Thevalveat position ¡®a¡¯ is reversed connected and supplied from thevalve conventionallyconnected at position ¡®b¡¯ ? Thecylindercan becontrolled from either position ¡®a¡¯ ¡®OR¡¯ position ¡®b¡¯ 1 2 4 5 3 14 12 2 4 5 1 3 14 12 a b
Single pulse control ? Each time the foot operated valve is pressed thecylinderwill single stroke + and - alternately ? First footoperation the cylinder movesout ? Second footoperation thecylinder moves in ? Third¡­.. outand soon 2 4 14 12 2 3 1 12 10 5 1 12 10 2 3 1 3 1 12 2 10
Air conservation ? Powerstroke in the instroke directiononly ? Differential area of the piston gives an outstroke force when the pressure is balanced ? Airused tooutstroke is equivalent toacylinderwith only thesame boreas the rod diameter ? Assumes the cylinder is not loaded on the plus strokeand low friction 2 4 1 5 14 12
Air conservation ? Powerstroke in the instroke directiononly ? Differential area of the piston gives an outstroke force when the pressure is balanced ? Airused tooutstroke is equivalent toacylinderwith only thesame boreas the rod diameter ? Assumes the cylinder is not loaded on the plus strokeand low friction 2 4 1 5 14 12
Double flow ? Wherea larger 3/2 valve is not available ? Two f low paths in a 5/2 valve each with a separate supply can bearranged togivedouble f loworsupply separate devices ? Ensure the tube size to the cylinder is large enough to take thedouble flow 4 2 12 14 5 1 3
Double flow ? Wherea larger 3/2 valve is not available ? Two f low paths in a 5/2 valve each with a separate supply can bearranged togivedouble f loworsupply separate devices ? Ensure the tube size to the cylinder is large enough to take thedouble flow 4 2 12 14 5 1 3
Counting ? Counting applications are bestachieved with electro- mechanical orprogrammable electroniccounters ? Pneumaticcounting circuits use large numbers of logic valvesand can be slow ? Thecounting chain shown will count to 4 ? Red and blue are non- overlapping alternatepulses, purple is the reset line 2 1 3 4
Counting application ? The counting circuit is applied tocount 4 strokesof a cylinder ? At restall counting valves are held reset by thestartvalve ? Startoutstrokes ¡®A¡¯ ? Alternatesignals from ¡®a1¡¯ and ¡®a0¡¯ progressesoperation of the counting valves up the chain ? On the 4th operation of ¡®a1¡¯ the green signal resets the startvalve tostop thecylinder A a0 a1 a0 a1 Start
3 c. industrial pneumatic circuit logic
Time delay ? A signal is restricted toslow the rateof pressure build up on a pressure switch (3/2 differential pressureoperated valve) ? When the pressure switch operates astrong un-restricted output is given ? A reservoirprovides capacitance toallow less fine and sensitivesettingson the f low regulatormaking iteasy toadjust 1 2 3 12 10 Signal in Output
Time delay ? Manual remotestartof a doubleacting cylinderwith a timedelay in theoutstroked position beforeautomatic return 2 2 4 5 1 3 14 12 3 1 12 10 - + A a1 2 3 1 12 10 a1 1 3 12 2 10
Pressure decay Manual remote start of a double acting cylinder Uses a low pressure operated valve connected normally open When the back pressure in the front of the cylinder falls below 0.1 bar the return signal is given Connection taken between the cylinder and f low regulator Useful for pressing work pieces of variable size 2 4 5 1 3 14 12 2 3 1 12 10 - + A a1 2 12 10 1 3 0.1bar
Electro-pneumatic The majority of systems use electrical/electronic control due to the high degree of sophistication and flexibility Solenoid valves are used to control cylinders Feedback signals are from reed switches, sensors and electrical limit switches Logic is hard wired or programmed in to a PLC (programmable logic controller) a0 a1 2 4 14 12 5 1 3 A ? Circuit building block for each cylinder a0 a1

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3 c. industrial pneumatic circuit logic

  • 3. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
  • 4. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 X Y Z 12 10
  • 5. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
  • 6. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 12 10 X Y Z 12 10
  • 7. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 X Y Z 12 10 12 10
  • 8. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 2 3 1 12 10 X Y Z 12 10
  • 9. Logic AND ? Toobtain theoutput Z both plungers X AND Y must be operated and held ? If X only isoperated theair will be blocked at port 1 in valveY ? If Yonly is operated therewill be no pressureavailableat port 1 ? If eitherX orY is released the outputsignal Z will be lost 2 3 1 12 10 2 3 1 12 10 X Y Z
  • 10. Logic AND ? This method must not be used as a two handed safetycontrol ? It is tooeasy toabuse. e.g. one of the buttonscould be permanently fixed down and the system operated from the other buttononly ? Use the purposedesigned two handed safetycontrol unit 2 3 1 12 10 2 3 1 12 10 X Y Z
  • 11. Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
  • 12. Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
  • 13. Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
  • 14. Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
  • 15. Logic OR ? Useof an ¡®OR¡¯ function shuttle valve ? SourceX and Ycan be remote from each otherand remote from thedestinationof Z ? When X orY is operated the shuttlevalve seal movesacross to prevent the signal Z from being lost through theexhaust of theothervalve Y Z 2 3 1 12 10 2 X 3 1 12 10
  • 16. Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
  • 17. Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
  • 18. Logic NOT ? A logic NOT applies to the stateof theoutputwhen the operating signal is present (the output is simply an inversionof theoperating signal) ? Thevalve shown is a normally open type (inlet port numbered 1) ? When thesignal X is present there is NOT outputZ ? When X is removed output Z is given 2 1 3 12 10 Z X
  • 19. Logic MEMORY ? A logic MEMORYallows the output signal state (ON or OFF) to be maintained after the input signal has been removed ? Any bi-stablevalve is a logic MEMORY ? With this leverdetented valve, once the lever has been moved X directionorYdirection it can be released and will stay in thatposition Z X 3 1 10 Y 12
  • 20. Logic MEMORY ? A logic MEMORY allows the output signal state (ON or OFF) to be maintained after thesignal thatset it has been removed Z X 3 1 12 10 Y
  • 21. Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
  • 22. Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
  • 23. Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
  • 24. Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
  • 25. Logic MEMORY ? A bi-stabledoublepilotvalve can be setorresetsimply bya pulse (push and release) on buttonsX orY Z 3 1 2 Y 3 1 12 10 2 X 3 1 12 10 12 10
  • 26. Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 10 12 2 1 3 12 10
  • 27. Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 12 10 2 1 3 12 10
  • 28. Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 12 10 2 1 3 12 10
  • 29. Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 2 1 3 12 10 12 10
  • 30. Logic MEMORY (latch) ? A popular memorycircuit is the latch ? Will not re-make after pneumaticpower failure ? A pulse on X operates the pilot / spring valve to give output Z ? A feedback from Z runs through the normallyopen valveY to latch theoperation of Z when X is released ? A pulseon Y breaks the latch and Z is exhausted X Y Z 3 1 2 3 1 12 10 2 1 3 12 10 12 10
  • 32. Logic circuits (spool valves) ? 5/2 OR ? Single pulse control ? Air conservation ? Double flow ? Counting ? NO / NC ? Selection / Diversion ? Latch ? OR, AND, NOT ? Single pulse maker ? Slow pressure build ? Pre-select
  • 33. 3/2 NO / NC ? A fully balanced valveallows pressureon any potor combinationof ports ? A singlevalvecan be used normallyopen or normally closed ? For normallyopen thesupply pressure is connected toport 1 ? For normallyclosed the supply pressure is connected toport 3 2 3 1 12 10 2 3 1 12 10
  • 34. 3/2 NO / NC ? A fully balanced valveallows pressureon any potor combinationof ports ? A singlevalvecan be used normallyopen or normally closed ? For normallyopen thesupply pressure is connected toport 1 ? For normallyclosed the supply pressure is connected toport 3 2 3 1 12 10 2 3 1 12 10
  • 35. 3/2 Valve selection / diversion ? Selection of one of two supplies connected toports 1 and 3 can be different pressures ? Diversionof one supply toone of twooutlets ? If it is required toexhaust the downstreamaira 5/2 valve is required 2 3 1 12 10 2 3 1 12 10
  • 36. 3/2 Valve selection / diversion ? Selection of one of two supplies connected toports 1 and 3 can be different pressures ? Diversionof one supply toone of twooutlets ? If it is required toexhaust the downstreamaira 5/2 valve is required 2 3 1 2 3 1 12 10 12 10
  • 37. Latch with controls ? In thisversionof a latch the push buttonvalves are connected toperform ¡®OR¡¯ and ¡®NOT¡¯ functions ? The ¡®OFF¡¯ valve must be placed last in the signal chain so that if bothvalvesare operated togetherthe ¡®OFF¡¯ command will dominateover the ¡®ON¡¯ command 2 3 1 12 10 2 3 1 10 2 3 1 10 ON 12 OFF 12 Out
  • 38. OR, AND, NOT ? A single 3/2 pilot operated spring returnvalvecan be use foranyof these logic functions ? x OR y gives output z ? x AND y gives output z ? x gives NOT z 3 1 12 10 12 10 12 10 AND OR NOT x y z 2 x 3 1 y z 2 3 1 x z 2
  • 39. Single pulse maker ? Convertsa prolonged signal x intoa single pulse z ? Signal z must be removed to allow thevalve to reset then x can beapplied again ? Thedurationof the pulsecan be adjusted with the flow regulator 2 3 1 12 10 x z
  • 40. Slow initial pressure build up ? Choosea 3/2 pilotspring valve with a relatively high operating forcee.g. 3 to 4 bar ? When the quick connect coupling is made, theoutput at port 2 is controlled at the rateof the f low regulator setting ? When the pressure is high enough tooperate thevalve full flow will takeover 2 3 1 12 10
  • 41. Pre-select ? The lever valve can pre-select the movement of the cylinder OUT or IN ? The movement will occur the next time the plunger valve is operated ? The plungervalvecan be released immediatelyand subsequently operated and released any numberof times 2 3 1 12 10 2 3 1 12 10 2 3 1 12 10 OUT/IN pre-select
  • 42. 5/2 OR function ? Thevalveat position ¡®a¡¯ is reversed connected and supplied from thevalve conventionallyconnected at position ¡®b¡¯ ? Thecylindercan becontrolled from either position ¡®a¡¯ ¡®OR¡¯ position ¡®b¡¯ 1 2 4 5 3 14 12 2 4 5 1 3 14 12 a b
  • 43. Single pulse control ? Each time the foot operated valve is pressed thecylinderwill single stroke + and - alternately ? First footoperation the cylinder movesout ? Second footoperation thecylinder moves in ? Third¡­.. outand soon 2 4 14 12 2 3 1 12 10 5 1 12 10 2 3 1 3 1 12 2 10
  • 44. Air conservation ? Powerstroke in the instroke directiononly ? Differential area of the piston gives an outstroke force when the pressure is balanced ? Airused tooutstroke is equivalent toacylinderwith only thesame boreas the rod diameter ? Assumes the cylinder is not loaded on the plus strokeand low friction 2 4 1 5 14 12
  • 45. Air conservation ? Powerstroke in the instroke directiononly ? Differential area of the piston gives an outstroke force when the pressure is balanced ? Airused tooutstroke is equivalent toacylinderwith only thesame boreas the rod diameter ? Assumes the cylinder is not loaded on the plus strokeand low friction 2 4 1 5 14 12
  • 46. Double flow ? Wherea larger 3/2 valve is not available ? Two f low paths in a 5/2 valve each with a separate supply can bearranged togivedouble f loworsupply separate devices ? Ensure the tube size to the cylinder is large enough to take thedouble flow 4 2 12 14 5 1 3
  • 47. Double flow ? Wherea larger 3/2 valve is not available ? Two f low paths in a 5/2 valve each with a separate supply can bearranged togivedouble f loworsupply separate devices ? Ensure the tube size to the cylinder is large enough to take thedouble flow 4 2 12 14 5 1 3
  • 48. Counting ? Counting applications are bestachieved with electro- mechanical orprogrammable electroniccounters ? Pneumaticcounting circuits use large numbers of logic valvesand can be slow ? Thecounting chain shown will count to 4 ? Red and blue are non- overlapping alternatepulses, purple is the reset line 2 1 3 4
  • 49. Counting application ? The counting circuit is applied tocount 4 strokesof a cylinder ? At restall counting valves are held reset by thestartvalve ? Startoutstrokes ¡®A¡¯ ? Alternatesignals from ¡®a1¡¯ and ¡®a0¡¯ progressesoperation of the counting valves up the chain ? On the 4th operation of ¡®a1¡¯ the green signal resets the startvalve tostop thecylinder A a0 a1 a0 a1 Start
  • 51. Time delay ? A signal is restricted toslow the rateof pressure build up on a pressure switch (3/2 differential pressureoperated valve) ? When the pressure switch operates astrong un-restricted output is given ? A reservoirprovides capacitance toallow less fine and sensitivesettingson the f low regulatormaking iteasy toadjust 1 2 3 12 10 Signal in Output
  • 52. Time delay ? Manual remotestartof a doubleacting cylinderwith a timedelay in theoutstroked position beforeautomatic return 2 2 4 5 1 3 14 12 3 1 12 10 - + A a1 2 3 1 12 10 a1 1 3 12 2 10
  • 53. Pressure decay Manual remote start of a double acting cylinder Uses a low pressure operated valve connected normally open When the back pressure in the front of the cylinder falls below 0.1 bar the return signal is given Connection taken between the cylinder and f low regulator Useful for pressing work pieces of variable size 2 4 5 1 3 14 12 2 3 1 12 10 - + A a1 2 12 10 1 3 0.1bar
  • 54. Electro-pneumatic The majority of systems use electrical/electronic control due to the high degree of sophistication and flexibility Solenoid valves are used to control cylinders Feedback signals are from reed switches, sensors and electrical limit switches Logic is hard wired or programmed in to a PLC (programmable logic controller) a0 a1 2 4 14 12 5 1 3 A ? Circuit building block for each cylinder a0 a1