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  • Automatic switching hydraulic valve

    I am going to build a device that uses a hydraulic cylinder that will move about 3/4". I want to feed a constant 2500 # of force at 25liters/minute to the device. The cylinder will be double acting so that when it reaches the end of it's stroke, it will automatically reverse and travel till it reaches the end of the opposite stoke. I want this to keep cycling back and forth till I turn off the feed line. Based on the volume of flow and the diameter of the cylinder I think it will run 30 to sixty strokes a minute. Is anyone familiar with a valve designed to do this or seen a mechanism to cause this type of action on a reliable basis? Thanks for your input.

    Wilhelm

  • #2
    I have not seen one, but I also have a similar application. I wanted to run a small pump (was thinking power steering pump) from an ac motor, then run the apparatus back and forth with the fluid. My concern was with the overlap while the valve was switching. I didn't want the fluid pressure to have a momentary peak everytime the valve switched, and on the other hand I didn't want it to become unloaded momentarily either. Before I shelved the project for the time being, I was thinking that a 'water hammer' reducer might become a part of the system.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #3
      The only way to do it is with limit stitches and electric valves.

      darryl, what you are looking for is called a hydraulic accumulator.

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      • #4
        You don't say what the bore is on the cylinder. Stroke is 3/4" correct? How many cylces do you want to have per minute and for what length of time is it to normally run?

        There are cylinders with built in limit switches. Especially for that small of a cylinder. Your electric vlave manifold will have a relief valve to avoid the spiking.

        More info please!
        Last edited by Black Forest; 10-24-2011, 04:38 AM.
        Location: The Black Forest in Germany

        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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        • #5
          Follow the design of the Westinghouse steam powered air compressor.

          http://www.nelsonslocomotive.com/Hei...ompressorI.htm

          A shuttle valve was directly shifted at the ends of the cylinder strokes.
          Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
          ~Practitioner of the Electromechanical Arts~

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          • #6
            does it have to be hydraulic? Why not a mechanical set up like old steam locomotives. Big wheel, short connecting rod and an electric motor to run it.

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            • #7
              Another thing we need to know. Does the speed of extend need to match retract speed?
              Location: The Black Forest in Germany

              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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              • #8
                Sixty strokes a minute is really a lot of fluid moving. Could this thing be spring return? If so, just copy and tweak any automotive brake system. If not, well, it does get a bit more complicated.

                What kind of force does it need?

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                • #9
                  There are proportional hydraulic valves-think Moog Hydrapoint- but they are complicated and hugely expensive.
                  Like others have said, it is probably cheaper to do it mechanically or with air.

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                  • #10
                    Hydraulic Reverse

                    I have a system like that on my surface grinder. There is a lever on the valve that is moved by an adjustable stop on the table. Every time the table goes by, the stop shifts the lever to the other side. It is simply a mechanical means of shifting the valve back and forth.

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                    • #11
                      I'm going to be running a 5" or 6" diameter hydraulic cylinder through a repetive 3/4" stroke. At 2500# of fluid pressure this will be about 50000 pounds at the end of the cylinder. This will be to run a small jaw crusher to reduce up to 4" rock to gravel. I suspect I cold use a two position valve and have a lever flop the valve fully to its opposite position when the cylinder reaches full travel limit. Just need to figure out the valve type terminology. I think this must be similar to how hydraulic concrete pumps work.
                      Last edited by 914Wilhelm; 10-24-2011, 11:50 AM.

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                      • #12
                        There are proximity switches for end of stroke on Hyd cylinders, they are a bit more expensive than the pneumatic variety that can sense anywhere on the stroke due to the cylinder being aluminum.
                        But if you want end of stroke detection these would work, Baluff are one manuf.
                        They could operate a simple relay flip flop circuit which would alternate the two solenoid coils on a double acting valve.
                        Max.

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                        • #13
                          This can be done hydraulicly, you want a cartridge valve. I believe you want a logic element valve. call www.hydraforce.com or www.sunhydraulics.com they will have what you need. they are relatively low priced.

                          you will need a relief valve in the system, and a cooler would be nice and quite a bit of oil at least 1 gal for every gpm flow, 2 would be better.

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                          • #14
                            Originally posted by MaxHeadRoom
                            There are proximity switches for end of stroke on Hyd cylinders, they are a bit more expensive than the pneumatic variety that can sense anywhere on the stroke due to the cylinder being aluminum.
                            But if you want end of stroke detection these would work, Baluff are one manuf.
                            They could operate a simple relay flip flop circuit which would alternate the two solenoid coils on a double acting valve.
                            Max.
                            You can do this with a dual solenoid valve that doesn't return to center when power is unapplied. Then you wire your end stroke limit switches such that when it gets to the end of stroke the other solenoid fires and it oscillates. Obviously your switches need to be rated to throw the solenoids or use a relay in between.

                            If you don't need super precision I'd jsut use two flow controls to control extend and retract speeds.

                            I've not done this with Hydraulics, but with pneumatics but the concepts should be the same. Obviously these hydraulics are alot more dangerous!

                            KEJR

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                            • #15
                              Is there any particular reason you're taking this tac instead of traditional rock crushing methods?

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