Appeal 2007-2807
Reexamination 90/006,511
Patent 5,156,811
shown in Figure 4, the flow control device of the invention will
be covered with the accumulated liquid, as a result of which it
will become substantially impervious to the flow of gas or
liquid through it. This therefore terminates the aspiration
before the accumulated liquid reaches the level at which
undesired outflow from the outlet fitting can occur.
Such a shut-off valve for controlling fluid flow is reasonably pertinent to the
problem with which the patentee was involved.
In the Background of the Invention section of the patentee’s
specification, the problems with which the inventor was concerned were
described. Specifically, they all involve contamination, during use, of
pipette devices for drawing and dispensing liquid samples. A major problem
is potential contamination by way of vaporized aerosol droplets and is
described as follows (Spec. col. 1:33-42):
One major problem with such liquid sampling
arrangements is that the pipettor or suction device itself may
become contaminated by a liquid sample, resulting in potential
hazards to operators as well as cross-over contamination in
subsequently drawn samples. One major cause of such
contamination is the so called aerosol effect, in which some of
the liquid sample is vaporized and forms droplets which are
drawn upwardly with the air as it is drawn out of the pipette by
the suction device.
A separate problem is contamination by contact with the liquid sample itself
and is described as follows (Spec. col. 1:42-47):
Such contamination can also occur if the operator holds the
pipette wrongly while drawing or transporting the sample, for
example at an angle rather than vertically, if the pipette is jarred
or moved too quickly, so that the liquid flows to the pipettor
end of the tube, or if the liquid foams or bubbles up the tube.
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