Help me with Hydraulics (info, links)

[esommer2500]

TDR masses:



I am working on a small presentation for the last project of my college career on spring-centered and detented directional control valves. Several hours of internet search has left me with nothing of use except the names of every hydraulic and valve manufacturer known to the web. What I am looking for would be an explanation of the aforementioned valves, and thier differences, schematics would be a wonderful thing.



Any links you might be able to provide would be worth thier weight in gold, otherwise it's off to the library. :{ TIA.



Eric



Guess I should say I already checked howstuffworks and tried several different search variations on the valve parts.

 

[esommer2500]

Thanks for the help! I was able to get some useful info from those sites.



I kind of figured it out for myself after thinking about it for awhile. A spring-centered valve will return to the neutral position when force is not applied to the lever. A detented valve will stay in the 'on' position until force is re-applied to the lever to overcome the force of the detent. I realized this after using our log splitter last weekend. To extend the ram to split, you have to hold the lever, but to return the ram back, the lever will 'hold' itself until it returns automatically. Sound reasonable?



Thanks again.



Eric

 

[Wayne M.]

Eric, You definetly have the basic idea. The directional valve, also known as a spool valve can control a hydraulic ram, motor or other device.

In the case of the ram, one variable that must be considered is weather it is single or double acting, as this effects the type of spool valve and circuit. In the case of the log splitter we are seeing a double acting ram since it has power extend and retract. In single acting rams (think a simple bottle jack) there is only power extend and gravity retract.

In the case of a double acting circuit, the spool valve must control supply and return and be able to invert these circuits to reverse direction.

There are many types of these valves, but the main categories are momentary and detent. It's how they are operated that adds to variety. Some are cable operated, some have electrical solenoids (think snow plow control), and some are operated by auxillary hydraulic and pneumatic circuits. Good luck with the presentation. I will continue to check around for schematics, If you must show a complete system, don't forget to include the resivoir, filter, pump, and most important-the main relief valve with return to tank. Here is one diagram showing a double acting circuit- http://www.indianafluidpower.com/ifpimages/systems.gif

 

[esommer2500]

Thanks alot for the additional information, I actually just got back from class, the presentation went fine. It only had to be about 4-5 minutes. This class has actually been pretty interesting, it focused on engines, hydraulics, and electic principles, with alot more engineering than I am used to. But it was nice to see how compression ratios, and all kinds of hydraulic calculations work out to real world applications.



Though I did have to educate the teacher in the diesel department. He couldn't seem to figure out how to tell the compressor from exhaust side on a turbocharger. :--)



Thanks again.



Eric