paper pickup mechanism

[rapiditup]

Hi there,
I hope someone can help me. I'm making a machine that needs to feed
sheets of standard 80g/m^3 office paper. Unfortunately i have to make
the mechanism myself, and have been looking inside some broken
printers. I have read that the cork like material at the bottom of the
tray has the function of separating just one page from the ream. I can
see how this might work when you get down to the last few pages,
causing a higher friction between the cork and the last page than the
friction between the top page and the page underneath. However when
there are a large number of pages it would seem that this cork has no
effect? Another printer had a small spring loaded lever that pressed up
against the front edge of the ream, but was easily pushed back by the
oncoming pages. This lever was not a single page detector switch, as it
was not wired to anything. What is the function of this lever?
Finally i noticed that when the paper tray pushes the pages up to the
roller, the sheets are rearranged with the front edge of the ream
vertical under the roller, is this angle something to do with the
single page separation also.

Thanks for any help given
regards:
Conor
Ireland

 

[Tony]

Hi there,
I hope someone can help me. I'm making a machine that needs to feed
sheets of standard 80g/m^3 office paper. Unfortunately i have to make
the mechanism myself, and have been looking inside some broken
printers. I have read that the cork like material at the bottom of the
tray has the function of separating just one page from the ream. I can
see how this might work when you get down to the last few pages,
causing a higher friction between the cork and the last page than the
friction between the top page and the page underneath. However when
there are a large number of pages it would seem that this cork has no
effect? Another printer had a small spring loaded lever that pressed up
against the front edge of the ream, but was easily pushed back by the
oncoming pages. This lever was not a single page detector switch, as it
was not wired to anything. What is the function of this lever?
Finally i noticed that when the paper tray pushes the pages up to the
roller, the sheets are rearranged with the front edge of the ream
vertical under the roller, is this angle something to do with the
single page separation also.

Thanks for any help given
regards:
Conor
Ireland

Connor
So far as I know the cork in the tray is simply to stop paper swilling about,
you are right in assuming it has nothing to do with separation.
In most inklet printers and some laser printers separation is achieved by
either a piece of cork immediately under the paper feed rollers or in some
cases by a spring loaded mechanism that has either cork or a rubber like
material on it, again underneath the feed roller(s). This sounds like the
second example you have mentioned, very little pressure is required and if the
pressure is too great it may prevent reliable feeding. Some laser printers use
extra rollers to achieve separation. Essentially the faster the paper feed the
more complex is the separation mechanism.
The angle of approach is critical in any printer to avoid the paper colliding
with the roller (or anything else) and to ensure that the paper is cleanly
picked up without damaging the leading edge.
By the way very few inkjets have any way of detecting the presence of paper in
the tray, this is done through a timing mechanism. The printer waits for the
paper to reach a paper sensor somewhere in the registration area and if the
paper does not get there in time it will post paper out. This explains why
paper out can occur when the printer misfeeds or there is a feed jam. Most
laser printers on the other hand do have a paper tray sensor.
Tony

 

[rapiditup]

Tony,
thanks for your comments
i think I'll have to do some more experimentation to gain a better
understanding of the separation mechanism.

regards
Conor