Is there a mechanical whizz out there who can satisfy my curiosity
about how the paper feed works in a laser printer?

More specifically, when the image printing has been completed, how
does the eject system know when to stop ejecting the paper?

Does it just keep ejecting until the end of the paper is sensed with
a photocell or does the 'page setup' data provide the control system
with the requisite information so that it can stop ejecting when the
paper *should* have cleared the transport mechanism?

So, for example, if you tell 'page setup' that you are printing a5 and
then feed in an a4 sheet, will the a4 sheet be left stuck in the
machine?

This relates to my earlier question about printing an a4 image at each
end of a long sheet of a4-width paper (not the same as 'banner'.

I believe that it varies from printer to printer, though a non-optical
sensor would have to be used in any laser printer which can cope with
transparency sheets (as almost all can). As a further option, I
believe that some printers have a sensor (again, almost certainly
non-optiical) on the input side which "measures the length of the
paper" as it goes through the imaging pathway. Printing a long
continuous sheet in a printer that had no specific setting for this
would almost inevitably make the printer believe that there was a
paper jam at some point in the process.

On Fri, 08 Oct 2004 07:36:00 +0100, John <(E-Mail Removed)> wrote:

>Is there a mechanical whizz out there who can satisfy my curiosity
>about how the paper feed works in a laser printer?
>
>More specifically, when the image printing has been completed, how
>does the eject system know when to stop ejecting the paper?
>
>Does it just keep ejecting until the end of the paper is sensed with
>a photocell or does the 'page setup' data provide the control system
>with the requisite information so that it can stop ejecting when the
>paper *should* have cleared the transport mechanism?
>
>So, for example, if you tell 'page setup' that you are printing a5 and
>then feed in an a4 sheet, will the a4 sheet be left stuck in the
>machine?
>
>This relates to my earlier question about printing an a4 image at each
>end of a long sheet of a4-width paper (not the same as 'banner'.


Please respond to the Newsgroup, so that others may benefit from the exchange.
Peter R. Fletcher

My experience is that the printer uses internal detection rather than
from a software indication of the paper length. I'd suspect either a
optical or tactile switch/sensor is used.

Art

John wrote:

> Is there a mechanical whizz out there who can satisfy my curiosity
> about how the paper feed works in a laser printer?
>
> More specifically, when the image printing has been completed, how
> does the eject system know when to stop ejecting the paper?
>
> Does it just keep ejecting until the end of the paper is sensed with
> a photocell or does the 'page setup' data provide the control system
> with the requisite information so that it can stop ejecting when the
> paper *should* have cleared the transport mechanism?
>
> So, for example, if you tell 'page setup' that you are printing a5 and
> then feed in an a4 sheet, will the a4 sheet be left stuck in the
> machine?
>
> This relates to my earlier question about printing an a4 image at each
> end of a long sheet of a4-width paper (not the same as 'banner'.

John wrote:
> Is there a mechanical whizz out there who can satisfy my curiosity
> about how the paper feed works in a laser printer?
>
> More specifically, when the image printing has been completed, how
> does the eject system know when to stop ejecting the paper?
>
> Does it just keep ejecting until the end of the paper is sensed with
> a photocell or does the 'page setup' data provide the control system
> with the requisite information so that it can stop ejecting when the
> paper *should* have cleared the transport mechanism?
>
> So, for example, if you tell 'page setup' that you are printing a5 and
> then feed in an a4 sheet, will the a4 sheet be left stuck in the
> machine?
>
> This relates to my earlier question about printing an a4 image at each
> end of a long sheet of a4-width paper (not the same as 'banner'.

Loosely speaking, the older HP laserjets use times and sensors.

The timer starts when the paper is ordered to advance into the printer.
After a specified time, if the paper hasn't exited the paper exit
sensor, then the jam condition is determined.

The paper size is typically set by settings on the paper tray. The tray
is set up for a size, and the printer senses this. Often the trays
accept only one size, and you can find bumps or other sensing locations
on the tray which tell the printer about the tray, and presumably the
paper in the tray.

Jim

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jbuch <(E-Mail Removed)> , and others wrote in response to my
question:

>> Is there a mechanical whizz out there who can satisfy my curiosity
>> about how the paper feed works in a laser printer?
>>

My thanks to all - does anyone happen to know how the Epson C1900
colour laser does it?

Apologies for not knowing the equivalent model in the US (or under
what brand this machinery is sold in the US - I don't see web evidence
for epson colour laser sales in the US.)