U.S. patent number 3,607,094 [Application Number 04/793,990] was granted by the patent office on 1971-09-21 for apparatus for pipetting and adding a liquid.
This patent grant is currently assigned to AB Autokemi. Invention is credited to Palle-Finn Beer.
United States Patent |
3,607,094 |
Beer |
September 21, 1971 |
APPARATUS FOR PIPETTING AND ADDING A LIQUID
Abstract
An apparatus for pipetting a liquid sample and supplying a
liquid reagent which comprises a pump cylinder, a pump piston
insertable in said pump cylinder, actuating means for said pump
piston, a tubular cannula connected to said pump cylinder for
drawing up a liquid sample, a conduit for supplying liquid reagent
to said pump cylinder, said conduit having provided therein a valve
means adapted to be actuated to its open position when the pump
piston reaches a position corresponding to an emptying of the pump
cylinder.
Inventors: |
Beer; Palle-Finn (Lidingo,
SW) |
Assignee: |
AB Autokemi (Stockholm,
SW)
|
Family
ID: |
20257459 |
Appl.
No.: |
04/793,990 |
Filed: |
January 27, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Jun 25, 1968 [SW] |
|
|
1020/68 |
|
Current U.S.
Class: |
422/63; 222/207;
73/864.22; 141/105; 417/446; 422/921; 73/864.12; 73/864.18; 141/25;
141/130; 417/443; 417/503; 422/923 |
Current CPC
Class: |
B01L
3/0206 (20130101); G01N 1/38 (20130101); B01L
3/0217 (20130101); G01N 35/1097 (20130101) |
Current International
Class: |
B01L
3/02 (20060101); G01N 1/00 (20060101); G01N
1/38 (20060101); B01l 011/00 (); G01n 001/14 ();
G01n 031/00 () |
Field of
Search: |
;23/253,259,292
;141/25,105,130 ;73/425.6 ;222/129.1,129.3,133,207
;417/443,446,503 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scovronek; Joseph
Claims
It is claimed:
1. An apparatus for pipetting a liquid sample and supplying a
liquid reagent which comprises a pump cylinder, a pump piston
insertable into said pump cylinder, a tubular cannula connected to
said pump cylinder, actuating means for displacing said pump piston
from said pump cylinder to draw liquid sample from a source and for
inserting said pump piston into said pump cylinder to discharge
said drawn liquid sample to a location other than said source,
means for moving said tubular cannula to said other location, a
conduit for supplying liquid reagent to said pump cylinder for
delivery through said tubular cannula to said liquid sample
location subsequent to discharge of said liquid sample, said
conduit being provided with a valve means, said valve means being
in closed position during said drawing and discharge of liquid
sample and in open position upon discharge of said liquid sample,
opening of said valve means being effected by said pump piston upon
insertion through said chamber, whereby the reagent can enter said
pump cylinder.
2. The apparatus of claim 1 wherein the valve means comprises a
valve element held in closed position by spring means and the pump
piston has the form of a rod-shaped displacement piston for lifting
said valve element from said closed position.
3. The apparatus of claim 1 wherein the actuating means comprises
an actuating piston slidably disposed and spring-loaded in a
housing, said actuating piston being connected to said pump, and
means for supplying compressed air to drive said actuating piston.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an arrangement in a pump for
pipetting a liquid sample and for adding a liquid reagent.
The invention is especially adapted for use in micropipetting, i.e.
when the pipetting takes place with volumes smaller than 15
microliters, but it is not restricted to this application and can
be used with advantage when it is a question of pipetting very
accurately determined volumes.
Particularly in micropipetting with the addition of a liquid
reagent it has proved difficult to achieve a constant pipetted
volume of liquid sample from one time to the next, which is partly
due to variations in volume of the flexible tube serving for
applying liquid reagent to the pipette. For example, the elasticity
of the tube and the variations in the time required for it to
return to its original volume after a stroke of the pump leads to
important variations in the overall volume owing to temperature
variations, hysteresis in the material of the tube, and movement of
the tube. These variations can be as high as several percent.
SUMMARY OF THE INVENTION
These difficulties are avoided according to the present invention
by means of a pump comprising a pump cylinder, a pump piston
insertable in said pump cylinder, and actuation means for said pump
piston, a tubular cannula connected to said pump cylinder for
drawing up a liquid sample, a conduit for supplying liquid reagent
to said pump cylinder, said conduit having provided therein a valve
means adapted to be actuated to its open position when the pump
piston reaches a position corresponding to an emptying of the pump
cylinder.
The valve means provided in the conduit preferably comprises a
valve element held in closed position by spring means. Opening of
the valve means may be achieved by employing as the piston pump one
having the form of a rod-shaped displacement piston and adapting
the piston rod to lift the valve element from its closed position
when the pump rod reaches the position corresponding to an emptying
of the pump cylinder.
The actuating means for the pump piston is preferably composed of
an actuating piston slidably disposed and spring-loaded in a
housing, the actuating piston being connected to the pump piston,
and means for supplying compressed air to drive the actuating
piston.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be described below with reference to the
attached drawing showing an embodiment of the pipetting
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The apparatus for the invention shown in the FIGURE is adapted to
transfer liquid sample from a test tube in a series 1 of test tubes
to another test tube in another series 2 of test tubes and for
supplying liquid reagent to the quantity of liquid sample thus
transferred. For instance, a certain quantity of liquid sample is
to be transferred from the test tube 3 of the first series to the
test tube 4 of the second series and liquid reagent is to be
supplied from a container 5. To this end, there is provided in the
apparatus a tubular cannula 6 which can be moved in a path
indicated by the dotted line 7 in a manner known per se, as shown
on the drawing. Cannula 6 is connected to a pump comprising a
cylinder 8 with a pump piston 9 insertable therein and preferably
having the form of a rod-shaped displacement piston. The pump
piston is connected to an actuating piston 10 provided in a
cylinder 11. A spring 12 urges the actuating piston 10 towards an
end position in cylinder 11. Actuating piston 10 can be brought
into the other terminal position against the action of spring 12 by
means of compressed air supplied from a compressed air source 13.
The supply of compressed air to cylinder 11 is controlled by a
valve means 14 which responds to a common control means 15 provided
for the apparatus. The stroke of actuating piston 10 can be
adjusted by means of a rod 16 which can be screwed to a variable
degree into an end wall of cylinder 11. The position of rod 16 can
be fixed with a lock nut 17 which may also serve as a sealing
between rod 16 and the end wall of the cylinder.
The compressed air acts on one side of actuating piston 10 and on
the other side thereof a constant pressure is maintained through an
aperture 18 provided in the wall of the cylinder.
The pump cylinder 8 communicates directly with the tubular cannula
6 and is also connected through a valve 19 with a conduit 20 for
supplying liquid reagent from container 5. This conduit also has
provided in it a pump 21 for the liquid reagent and a valve means
22 which is controlled by control means 15.
The valve member 23 of the valve 19 is held by a spring 24 in
seated position and can be unseated against the action of spring 24
by the pump piston 9 pushing against valve member 23 in the
position of the pump piston corresponding to a complete emptying of
the pump cylinder.
The operation of the apparatus will now be described. First,
however, it should be noted that the test tubes of series 1 and 2
are not drawn to the same scale as the pump which has been enlarged
on the drawing in the interest of clarity. Also, the entire unit
comprising pump 8, 9 and actuating pump 10, 11 is adapted for
movement together with tubular cannula 6 so that the latter can be
attached to pump 8, 9 in a fixed manner. On the other hand,
flexible portions 25 are provided in the connection between valve
14 and actuating cylinder 11 as well as between valve 22 and valve
19.
With the pump piston 9 in the uppermost position with reference to
the drawing, cannula 6 is lowered into test tube 3 after which
valve means 14 is actuated by control means 15 to a position in
which the compressed air does not act on actuating piston 10. The
latter is then brought by spring 12 to the lowermost position with
reference to the drawing as defined by rod 16. This causes a
predetermined quantity of liquid sample to be drawn into cannula 6
corresponding to the displacement of piston 9, and during this
movement of the piston valve 19 remains closed whereby the quantity
of liquid sample that is drawn into cannula 6 is determined
exclusively by the displacement of the piston in cylinder 8.
Cannula 6 is then moved along the path shown in dotted lines to
test tube 4 and valve means 14 is actuated by control means 15 so
as to cause compressed air again to be supplied to the pump.
Actuating piston 10 with pump piston 9 are then displaced against
the action of spring 12 to the uppermost position and the quantity
of liquid sample drawn into cannula 6 is emptied into test tube 4.
When the pump piston 9 has reached the topmost position, with
reference to the drawing, it reached valve member 23 and causes it
to be unseated. Simultaneously, or after this, control means 15
actuates the other valve means 22 causing the connection between
liquid reagent pump 21 and conduit 20 to be established. Pump 21 is
now made to supply a predetermined quantity of liquid reagent which
flows through conduit 20 and valve 19 down into cylinder 8 and
tubular cannula 6. Simultaneously, with the supply of liquid
reagent to the liquid sample in test tube 4, the interior of
cannula 6 is rinsed from possibly remaining traces of liquid
sample. Cannula 6 is then transferred to the other test tube in
series 1 after which the sequence of events just described is
repeated.
To reduce still further the danger of an undesired transfer of
liquid sample from one sample to another, it is possible,
simultaneously with the supply of liquid reagent in the manner
referred to above, to cause a rinsing of the exterior of cannula 6
by supplying liquid reagent via a branch conduit 26 of conduit 20
to an annular nozzle 27 placed around cannula 6. By suitable
dimensioning of branch conduit 27 relative to the path leading
through cannula 6, it can be achieved that a suitable quantity of
liquid reagent causes the desired rinsing of the exterior of
cannula 6.
In the embodiment of the invention shown, movement of actuating
piston 10 in one sense is limited and adjusted by means of rod 16.
Movement in the other sense is limited by means of the interior
surface of the terminal wall of the piston contacting the free end
of the tube 28 which is screwed into the upper end wall of cylinder
11. The length of tube 28 is selected so as to cause pump piston 9
to unseat valve member 23 at the precise moment when actuating
piston 10 is stopped by tube 28. As indicated in the drawing, the
upper end of the tube is arranged to hold a sealing O-ring in
contact with pump piston 9.
* * * * *