Homebrew PCBs

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.