Improvements in Pipettes for Automatically Measuring off Small Quantities of Liquid.
Year: 1897

page_text: Date of Application, 25th Sept., 1897
Complete Specification Left, 27th June, 1898-Accepted, 30th July, 1898
PROVISIONAL SPECIFICATION.
Improvements in Pipettes for Automatically Measuring off Small
Quantities of Liquid.
We, ALFRED WALTER STOKES, F.C.S., F.I.C., of 60, Parkhill Road, Haverstock
Hill, Hampstead, London, Public Analyst and Analytical Chemist, and R. A.
LISTER & CO. LIMITED, of Victoria Iron Works, Dursley, Gloucestershire, Engineers
of this invention to be
and Ironfounders, do hereby declare the nature
follows:-
as
For accurate measurement the apparatus may be said to consist of an ordinary
shortnosed pipette terminating at the upper limit of the chamber or part for con-
At this place a conical valve seat is
taining the quantity of liquid to be measured.
The valve has a stem rod or lever for
provided for a plug or valve ground to fit it.
operating it and is by preference provided with a helical or other spring for holding
the valve open.
In one form the chamber is continued into a tube surrounding the stem the upper
end of which passes out through a cork in its upper end for guiding the stem ;---this
tube where it joins the chamber has one or more lateral openings.
When the pipette is placed in a vessel containing enough liquid to cover it it
will fill from below the air passing out through the lateral openings. By depressing
the valve stem with a finger the valve is brought into its seat and the pipette in this
condition can be raised out of the liquid any surplus liquid above the valve having
first been allowed to flow out through the lateral openings. The pipette is brought
over the vessel to be charged and the finger pressure is taken off the valve stem the
valve will then be opened by the spring and the air entering the valve by the
lateral openings will allow the measure of liquid in the pipette chamber to be
discharged.
By a reverse arrangement the spring may be adapted to hold the valve in its
seat, and the stem would then have to be raised against the pressure of the spring
while filling and also when emptying.
Or instead of the surrounding tube a rod may be affixed to the side of the pipette
and the valve stem be guided and held in position by side projections and one or
more springs or elastic rings.
Where less accurate measurement is needed the pipette is combined with the
On the upper end of the pipette is
supply bottle to form a stopper therefor.
provided a valve in the form of a rubber bulb or teat of the capacity required to be
drawn off and just below this the pipette passes through a cork which forms the
stopper for the supply bottle. The lower end of the pipette reaches to the interior
5 bottom of the bottle. To draw up the quantity of liquid the teat is flattened between
a finger and the thumb and then released whereupon the liquid will fill the pipe to
the required extent and be retained therein so that the pipette can be taken out of
the bottle and discharged into the receiving vessel by again squeezing the feat or

page_text: bulb. The quantity to be drawn off can be varied within certain limits by forcing
the tube more or less into the teat.
das of Santambon 1907
Improvements in Pipettes for Automatically Measuring off Small
Quantities of Liquid.
We, ALFRED WALKER STOKES, F.C.S. F.I.C.. of 60, Parkhill Road, Haverstock Hill,
Hampstead, London;. Public Analyst and Analytical Chemist, and R. A. LISTER AND.
COMPANY, LIMITED, of Victoria Iron Works,. Dursley, Gloucestershire, Engineers and*
Ironfounders, do hereby declare the nature of this invention and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement :-
This invention relates to apparatus for accurately measuring off a given quantity.
of liquid and may be said to consist of an ordinary shortnosed pipette cut off at the
upper limit of the chamber or part for containing the quantity of liquid to. be
measured at which place a conical valve seat is provided for a plug or valve which
is ground into said seat. This valve has a stem rod or lever for operating it and is by
preference provided with a helical or other spring for holding the valve open.
In one form of the apparatus a tube is provided on the top of the chamber, integral
therewith and surrounding the valve seating and the valve stem the upper end of
which passes out through a cork in the upper end of the tube. This tube where it
joins the chamber has one or more lateral openings.
When the pipette is placed in a vessel containing enough. liquid to cover it, it will
fill from below the air passing out through the lateral openings in the tube. By
depressing the valve stem with a finger the valve is brought into its seat and the
pipette can in this condition be raised out of the liquid, any surplus liquid above
the valve having first been allowed to flow out through the lateral openings in the
tube. The pipette is brought over the vessel to be charged and the finger pressure
is taken off the valve stem, the valve will then be opened by the spring and the air
entering the valve by the lateral openings in the tube will allow the measure of liquid
in the pipette.to be discharged.
.
'
By a reverse arrangement the spring may be adapted to hold the valve in its seat
and the stem would then have to be raised against the pressure of the spring while
filling and also when emptying.
Instead of the surrounding tube a rod may be affixed to the side of the pipette
and the valve stem may be guided and held in position by side projections and one
or more springs or elastic rings.
Referring to the drawings.
Fig. 1 is a sectional elevation of one form of pipette according to our invention.
Fig. 2 is an elevation partly in section of another form of pipette according to our
invention.and. Fig. 3 is a.sectional plan thereof.
Fig. 4 is an elevation of a third modification of pipette according to our invention
and Fig. 5 is a sectional plan thereof on the line 5-5 Fig. 4, and Fig. 6 a sectional
plan thereof on the line 6-6 Fig. 4.
A Fig. 1 is the chamber for containing the quantity of liquid to be measured off
at one operation. In its upper end it is provided with.a conical valve seating B into
which fits the valve C: D. is a tube integral with the chamber A and is provided at
its lower end with two or more lateral openings D¹ so formed as to permit the surplus

page_text: iquid to flow off readily from the top of the chamber A.
This tube D surrou
The
tem E of the valve C and is of sufficient size internally to permit of the valve being
readily inserted and withdrawn and easily cleaned. The upper end of the stem Ĕ
passes through and is guided by a cork F in the upper end of the tube D.
helical spring G attached to the stem E and the cork F tends to pull the valve out
of its seat. Fis a small vent or passage in the cork.
In the modification shown in Figs. 2 and 3 the valve stem E is not surrounded by
a tube but guided between forks D² on a rod D which proceeds from the top of the
chamber A the stem being held up to the rod by rubber bands H. Small rubber
rings I on the stem E hold said stem and rod D elastically apart; all the parts being
of glass.
The spring G which keeps the valve C out of its seating acts between the top
In Figs. 4, 5, and 6 the support D is shown
forks D2 and a knob E¹ on the stem E.
crescent shaped in section and half surrounds the stem E. The spring G acting
between the top of the support D and the knob E¹ keeps the valve C out of its
seating.
The
The pipette when placed in a vessel containing enough liquid to cover it, will fill
from below, the air passing out through the valve and the lateral openings D¹ Fig. 1.
By depressing the valve stem E with a finger the valve C is brought into its seat
and the pipette can in this condition be raised out of the liquid, any surplus liquid
above the valve having first been allowed to flow out through the openings D¹.
pipette is brought over the vessel to be charged and upon the finger pressure being
taken off the valve stem, the valve will be opened by the spring and the air entering
the valve (by the openings D¹ in the form shown in Fig. 1) will allow the measure
5 of liquid in the chamber A to be discharged.
Pipettes constructed according to our invention are easily kept clean (the valve
being also easily removable for cleaning) and the valve being kept normally out of
its seating by the spring is not liable to become set fast when the apparatus is out
of use for a long period. The exact quantity of liquid is measured rapidly and is at
30 once discharged by simply releasing the finger pressure.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. A pipette consisting of a measuring chamber a valve seating in the upper end
35 thereof, an upward continuation of the measuring chamber, a valve and stem guided
in said continuation and a spring for holding said valve normally open substantially
as and for the purpose set forth.
2. The constructions of pipette shown in the drawings.
1808