not having a common center; not concentric; "eccentric circles"
www.cogsci.princeton.edu/cgi-bin/webwn

The general term "eccentric" refers to two circles whose center is not at the same point. The primary bicycle usage refers to the special bottom brackets used on better tandems and some other cycles, which allows the bottom bracket to be moved slightly for purposes of fine-tuning chain length. A tandem synch chain runs between two bottom brackets, and the front bottom bracket is usually mounted in an eccentric. This is a cylindrical part with a large hole running parallel to its axis. This hole is sized and threaded to accept a normal bottom bracket assembly. The cylinder mounts into an oversized shell located where a normal bottom bracket would be. The outer shell may use pinch bolts or setscrews to secure the moveable eccentric cylinder in position. Some eccentrics use a wedge bolt system, similar to that of a handlebar stem, so secure the cylinder. For more details on this, see my article on Adjusting Tandem Synch Chains.
www.sheldonbrown.org/gloss_e-f.html

'eccentric' in a paper/pulp context comes up as parts of a motor (e.g. mechanism, shaft, etc)

I don't get the 'masses' as it seems to refer to the paper/pulp, not the machine. Yet there are hits for "eccentric mass", referring to the way weight is distributed, but just one for 'eccentric mass drive/motor'. See below.

Hits also for 'eccentric press drive' and 'eccentric motor'

some particular considerations can make the vibrotactile device simple with a low production cost, for those embodiments with such cost constraints. For example, a stock eccentric mass motor can be used to take advantage of existing supplies of these motors. The motor drivers should be assumed to operate uni-directionally, since that is the most common type of motor operation in current vibrotactile devices.http://appft1.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=...

In the vibratory system context you have this:

Eriez Magnetics
Syncro-Sieve - Vibratory Screeners Weight adjustment on eccentric motor. Similar to the syncro-sizer, the syncro-sieve instead uses an eccentric weighted motor to achieve vibration. Weights are adjustable to change pattern flow and retention time. (read more)
(more product announcements from Eriez Magnetics) http://www.google.es/search?q=cache:GYy3B7vAqg4J:process-equ...|lang_en|lang_fr|lang_de|lang_pt|lang_es

This is a minerals context, a sieve, but maybe that's what your machine does, sieve out particles.




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Note added at 46 mins (2004-10-11 11:56:34 GMT)
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I think the naswer is in the last ref: eccentric weighted motor.

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Note added at 47 mins (2004-10-11 11:57:06 GMT)
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I would up my confidence level to Medium now:-)