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Hydraulic Pusher

Created by: nbk at: 10/23/2010 10:20 AM (8 Replies)

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10/23/2010 10:20 AM	Rate (0)
nbk Posts: 197 Rating: (3)	Dear all, In a typical hydraulic pushing application do you activate the valve and pump together or they come one-after-another with a certain delay? And do you need to know what kind of valve is in use for a particular application ............ like there are times when the cylinder extends (moves forward) when pump & valve both are energized , but retracts(comes reverse) with only pump running and valve de-energized ............. and in some cases the hoist movement has "fast" and "slow" speed because the hydraulic cylinders has 2set of valves for "fast" and "slow" movement which receives different commands ......... and in few applications there are 2 different valves for "forward" and "reverse" movement. Regards
nbk Posts: 197 Rating: (3)
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11/10/2010 1:25 PM	Rate (0)
SINAMICS_TO Bronze Member Joined: 4/24/2008 Last visit: 8/2/2024 Posts: 213 Rating: (16)	Pleasespecify your question. For a hydraulic axis you can use a CPU31xT. With this module it is very easy to couple/sync hydraulic axis together.

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11/10/2010 3:04 PM	Rate (0)
nbk Posts: 197 Rating: (3)	Dear Böhser_Onkel, Thanks for the reply (only yours after so many days!!) As I said its a typical hydraulic cylinder application (forward & reverse movement OR up & down movements for a machine) used in factories (not in context of a dedicated CPU31XT) ....... I just want to know what is the usual practice (or if there is a standard rule) to engage the pump & valve together or there is a certain delay between them ? Regards
nbk Posts: 197 Rating: (3)
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11/11/2010 9:38 AM	Rate (0)
SINAMICS_TO Bronze Member Joined: 4/24/2008 Last visit: 8/2/2024 Posts: 213 Rating: (16)	Based on my state of knowledge there is no standard rule for this case. I think it depends on your physical hardware. If I understand your application in the right way (you use only one hydraulic axis and you do not want to sync some axis together), there should be no delay between pump and valve.

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11/11/2010 9:16 PM	Rate (0)
nbk Posts: 197 Rating: (3)	Thank u Böhser_Onkel
nbk Posts: 197 Rating: (3)
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1/16/2011 3:15 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	It depends on how valves are mounted on a hydraulic pump. If you don't have a bypass valve on hydraulics to limit pressure than I would say to control valves and pump instantly, if there exists all neccessary protection elements in your hydraulic system then you first turn on the pump and for a while you engage control valves. After few minutes that valves are not being actuated, tur off the pump. Or more likely: you have a start/stop button for a pump, you have an extra bypass valve normaly open to circulate and star/delta contactor to power the pump. First you have to start in star connection and then to delta, after that you engage bypass valve to pressurize the system. When the system will reach the setpoint pressure on bypass valve (secod one withoun coil, analogue) the oil will circulate trough this valve, you don't need to turn pump off even if the cylinders are still. You can now move cylinders as you wish, after finishing the job the operator pushes stop button of pump and it is done.

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1/16/2011 10:49 PM	Rate (0)
nbk Posts: 197 Rating: (3)	Thank you very much Marko Bursic for your detailed explanation.
nbk Posts: 197 Rating: (3)
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1/18/2011 11:32 AM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	I also forgot the hydraulic lifting: you could have only to activate the pump trough some non-return valve when lifting . For lowering you cold use a hydraulic valvefor oil return from cylinderin the reservoir, the weihgt of a lift would make the presure in the cylinder, so you don't need a pump to lower the lift.

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1/18/2011 2:31 PM	Rate (0)
nbk Posts: 197 Rating: (3)	Thanks again Marko Bursic. I remember in our factory there was a hydraulic pusher that used to extend (forward) when the pumpANDvalve were energized but it used to retract (reverse) with ONLY pump running (the valve was no longer on power) ................. How does the piston reverses with only the pump in motion OR What exactly brings back the piston so that the cylinder stops at its home position which is limit switch "pusher reverse off" ?? ..... I'm just a bit curious to know ... though you may consider these queries coming from a new comer !! REGARDS
nbk Posts: 197 Rating: (3)
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