Well this is interesting. The original patent paper clearly states
that the etchant is pumped up the tube using a sprial mounted inside
the tube. This sounds reasonable to me but unfortunately will be
close to impossible to fabricate such a spiral. Somebody who has at
least a middle-sized lathe could probably try to turn it out of a
plastic bar, similar to turning a thread. I think I'll try the 3-
hole type next.
Regards
Martin
--- In
Homebrew_PCBs@yahoogroups.com, Adam Seychell
<a_seychell@y...> wrote:
> Phil wrote:
> > --- In Homebrew_PCBs@yahoogroups.com, Markus Zingg
<m.zingg@n...>
> > wrote:
> >
> >>Bungard, but since it dates back to the sixties I figure the
patent
> >>protection is meanwhile void. I'm however not experienced, that
> >
> > said I
> >
> >>don't know if a patent is protecting "forever" or if it's only
> >>effective for some years.
> >>
> >
> >
> > 17 years
> >
>
> we had patent discussion long time ago on this group.
> see message
> http://groups.yahoo.com/group/Homebrew_PCBs/message/1561
>
> Does the yahoo groups "search archive" feature search the entire
hystory
> of the messages ? I coulnd't find this message using the yahoo
search.
> All the messages are stored, but it seems they cannot all be
searched. I
> had to search for this message from the email folder on my home PC.