Hydraulic proportional control valves...

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bushtor's Avatar (by Gravatar)bushtor posted on
June 3, 2010, 6:05 am
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Hi,

If this is not the proper group, where should I post such a topic?

I have a smail tractor mounted hydraulic crane where the control valve
assembly is a bit worn.  Instead of just spending a lot of money in
getting a suitable 'manual' control valve assy I consider checking a
bit around to see if I can find a surplus electric proportional
hydraulic control valve assy for at least 4 double-acting cylinders
and replace my old control valves with this electric version. (I don't
want wireless remote control, only wire)...

Are there different types of electric proportional valves for doible-
acting cylinders or would almost any model do?  (Given that flow and
pressure are supported).

However despite that I work a lot with electronics I don't know how
the solenoids normally are interfaced with the control pots.  Do they
use an electronic module between the joysticks and the solenoids which
varies the current between the solenoids according to the position of
the joystick, or is this circuitry normally included in the joystick
assy?  Thanks for some comments on this.

Does anyone here have suggestions on where to obtain such surplus
equipment?

Other relevant comments and suggestions are highly appreciated :-)

regards Tor

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Jerry Avins's Avatar (by Gravatar)Jerry Avins posted on
June 3, 2010, 11:26 am
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Re: Hydraulic proportional control valves...



On 6/3/2010 6:05 AM, bushtor wrote:

You want to undertake what will turn out to be a research project with a
good amount of trial and error before you get it right. If you have the
time for such a project, fine. I would suggest looking at the service
and operating manuals for a unit you know, and talking to the mechanics
at a tractor dealership. You can bake a better decision when you know
more about the scope of your proposed project.

Jerry
--
Engineering is the art of making what you want from things you can get.
ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ

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BillB's Avatar (by Gravatar)BillB posted on
June 3, 2010, 3:53 pm
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Re: Hydraulic proportional control valves...



Hi Tor

Proportional hydraulic directional control valves come in two basic designs,
those where the spool has a linear measuring transducer fitted to allow
close loop control of the spool position. This gives a more accurate control
of the cylinder speeds, with better repeatability. The second type do not
have any feedback system, but rely the force generated by the solenoid
depressing a spring at the opposite end of the spool, until a balance
position is reached to give a spool position the will give the control of
flow. Both types of valve are available in both single and two stage
configuration. A two stage valve is one where the valve has a small pilot
control valve which then controls the position of a main spool to control
the flow to the cylinder. See
http://hydraulics.eaton.com/products/valves_proportional_directional_controls.htm
Both types of valve require an amplifier to control the current supplied to
the solenoid coils fitted to the valve, these can be simple current
controllers or fully closed loop controls, again see the Vickers site for
more information.

As suggested by Jerry talk to your local dealers before you commit yourself.

--
BillB

Leeds Lad in exile

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