Subject:
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Re: pneumatic cylinder: why not hydraulic ??
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Newsgroups:
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lugnet.technic
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Date:
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Thu, 8 Apr 2004 21:24:40 GMT
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Viewed:
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2974 times
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In lugnet.technic, Kevin L. Clague wrote:
> In lugnet.technic, Kevin L. Clague wrote:
>
> <snip>
>
> >
> > I have created a pneumatic polarity reversor using four pneumatic switches.
> >
> > I did an analysis and my pneumatic multiplexor works as a hydraulic switch that
> > does not have a free release.
> >
> > http://www.brickshelf.com/gallery/kclague/Computing/p5280146.jpg
> >
> > The above picture contains two pneumatic multiplexers. One facing us, and the
> > other away from us. For example, the gray hoses work with one mux, the black
> > (on the opposite face) work with the other.
> >
> > I use these to do the polarity reversing needed to make my pneumatic quadraped
> > and hexapods be able to modify their walking behavior.
> >
> > The interesting thing to note is that no matter what way the switches are
> > flipped there is no release. Using one of these muxes gives you a hydraulic
> > switch with *no free release*.
>
> Actually this multiplexer is more efficient because it uses less parts:
>
> http://www.brickshelf.com/gallery/kclague/Computing/p6050069.jpg
>
> Kevin
I get the impression you've complicated things by putting different switches at
different lever angles. My reverser idea puts the switch lever pivots 16mm
apart, all in a line with 2-beams between: BSBSBSBSB along a beam of length 17
holes, so an 8-beam and a 10-beam with plates above and below should suffice.
The levers have toggle joints on top, with a 14-beam connecting them. This beam
can be pushed by 2 cylinders if required. All the switches move together over
their full movement range.
This reverser deliberately sends air from the unpowered side of the cylinder
back to the unpowered input hose, with no leaks to the atmosphere. It is just
as important to release air correctly as it is to not release it incorrectly!
These reversers can be daisy-chained and so a single switch can provide the
first stage of reversal, forming an exclusive OR gate. This is useful because
the single switch can be mounted on the end of a robot arm, whereas the 4
switches are too heavy and need to be on the base. On my pick and place robot
they sit on the base, pushed by cylinders in parallel with the grab, so they
form a counterweight. The grab is an easier load, so it always moves first.
Of course the new switches can be closer together, so only a 12 beam is required
for 10 holes, and 1 14-beam for 12 holes to mount the switches.
The only place I've used offsets between switch lever angles is in pneumatic
steering, when I want to get cylinders to stop half way. My other gates have
the switch levers all at the same angle, 'cos you know that all switches will
block or pass air at the same time.
Mark
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Message has 1 Reply:
 | | Re: pneumatic cylinder: why not hydraulic ??
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| (...) I'd love to see a picture of your reversor, as verbal explanations by themselves are often much harder to comprehend. (...) Again, I'd like to see this. My pneumatic mux that can act as a polarity reversor, can just as easily be used for an (...) (20 years ago, 8-Apr-04, to lugnet.technic)
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