Andrew May wrote:

In the meantime dos anyone have any ideas about the purpose of the
spring. It can be seen at the bottom of the photograph on page six of
the document here if anyone is interested.

http://www.vad1.com/photo/dirty-scan...2000-cleaning/

Note: that this is the LS-2000 but the mechanism looks almost
identical.

I would guess it's there to remove any free play in the drive system. That
is, make sure that the there's no microscopic movement caused by there being
no loading on the gears at any point. (There's a proper technical term for
this but I'm darned if I can remember what it is at the moment. Whiplash
maybe)

Tim