U.S. patent number 3,802,608 [Application Number 05/242,669] was granted by the patent office on 1974-04-09 for liquid metering device with concentric pistons and unidirectional liquid flow.
This patent grant is currently assigned to Packard Instrument Company, Inc.. Invention is credited to Robert C. Gullett.
United States Patent |
3,802,608 |
Gullett |
April 9, 1974 |
LIQUID METERING DEVICE WITH CONCENTRIC PISTONS AND UNIDIRECTIONAL
LIQUID FLOW
Abstract
A liquid metering device is provided for transferring a measured
batch of liquid from a supply container. The device includes an
outer casing and an inner casing located within the outer casing
and defining an annulus therebetween. A first piston is located in
the annulus for sliding movement therein in response to fluid flow
in and out of the annulus. A spring is provided within the outer
casing for urging the first piston into an upper position, means is
provided for directing fluid flow into the annulus to actuate the
first piston into a lower position in opposition to the spring. A
second piston is located within the inner casing for sliding
movement therein, and is secured at its lower end to the first
piston so that the first and second pistons move within their
respective casings in unison. The second piston and inner casing
define therebetween a liquid chamber in communication with a liquid
outlet. Liquid communication means is provided between the liquid
supply container and the liquid chamber. Upon actuation of means
provided for terminating fluid flow into the annulus and for
venting fluid contained therein to atmosphere, the pistons are
moved to an upper position in response to the spring so that liquid
is discharged from the liquid chamber into the liquid outlet.
Inventors: |
Gullett; Robert C. (Romeoville,
IL) |
Assignee: |
Packard Instrument Company,
Inc. (Downers Grove, IL)
|
Family
ID: |
22915724 |
Appl.
No.: |
05/242,669 |
Filed: |
April 10, 1972 |
Current U.S.
Class: |
222/309;
417/402 |
Current CPC
Class: |
G01F
11/04 (20130101) |
Current International
Class: |
G01F
11/04 (20060101); G01F 11/02 (20060101); G01f
011/06 () |
Field of
Search: |
;222/309,253,259,389,260,261,390 ;417/402 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reeves; Robert B.
Assistant Examiner: Kocovsky; Thomas E.
Attorney, Agent or Firm: Wolfe, Hubbard, Leydig, Voit &
Osann, Ltd.
Claims
I claim as my invention:
1. A device for transferring a metered batch of liquid from a
supply container comprising, in combination, an outer casing, an
inner casing located within the outer casing and defining an
annulus therebetween, a first piston located in the annulus for
sliding movement therein in response to fluid flow in and out of
the annulus, spring means within the outer casing for urging the
first piston into an advanced position, means for providing fluid
flow into the annulus to move the first piston into a retracted
position in opposition to said spring means, a second piston
located within the inner casing for sliding movement therein and
secured at one end to the first piston so that the first and second
pistons move within their respective casings in unison, said second
piston and inner casing defining therebetween a liquid chamber in
communication with a liquid outlet, liquid communication means
extending between the liquid supply container and the liquid
chamber, a first check valve between said liquid supply container
and said liquid chamber for passing liquid from said supply
container to said chamber during retracting movement of said
pistons and for blocking the flow of liquid from said chamber to
said supply container during advancing movement of said pistons, a
second check valve connected to said liquid outlet for passing
liquid discharged from said liquid chamber via said outlet during
advancing movement of said pistons and for blocking the flow of
liquid into said chamber via said outlet during retracting movement
of said pistons, and means for terminating fluid flow into the
annulus and venting fluid contained therein to atmosphere whereby
the pistons are moved to an advanced position in response to the
spring means so that liquid is discharged from the liquid chamber
into the liquid outlet.
2. The device of claim 1 in which the liquid communication means
includes a flexible tube located within the spring means and
provided with a loose knot having the mean slope of the knot
arranged opposite to the spiral of the spring.
3. The device of claim 1 in which means is provided for adjustably
limiting the stroke of the pistons to thereby limit the volume of
liquid transferred to a predetermined volume.
4. A device for transferring a metered batch of liquid from a
supply container comprising, in combination, an outer casing, an
inner casing located within the outer casing and defining an
annulus therebetween, a first piston located in the annulus for
sliding movement therein in response to fluid flow in and out of
the annulus, spiral spring means within the outer casing for urging
the first piston into an upper position means for providing fluid
flow into the annulus to actuate the first piston into a lower
position in opposition to said spring means, a second piston
located within the inner casing for sliding movement therein and
secured at its lower end to the first piston so that the first and
second pistons move within their respective casings in unison, said
second piston and inner casing defining therebetween a liquid
chamber in communication with a liquid outlet, liquid communication
means extending between the liquid supply container and the liquid
chamber, said liquid communication means including a flexible tube
located within the spring means and provided with a loose knot
having the mean slope of the knot arranged opposite to the spiral
of the spring means and means for terminating fluid flow into the
annulus and venting fluid contained therein to atmosphere whereby
the pistons are moved to an upper position in response to the
spring means so that liquid is discharged from the liquid chamber
into the liquid outlet.
Description
DESCRIPTION OF THE INVENTION
The present invention relates generally to a liquid pumping device,
and more particularly to such a device for pumping adjustably
metered batch quantities of liquid.
The device of the present invention is particularly useful for
pumping metered batch quantities of various liquids used in
apparatus for the preparation of samples for radioactive isotope
tracer studies. Such liquids include liquid scintillators and
liquid trapping agents for carbon dioxide. A sample preparation
apparatus with which the liquid metering devices of the present
invention are particularly useful is described and illustrated in
pending Kaartinen Applications Ser. No. 242,481 filed April 10,
1972.
It is a primary object of the present invention to provide an
improved liquid metering device which efficiently pumps batch
quantities of liquids of pre-selected size, even when the liquid
quantities amount to only a few milliliters or less. A related
object is to provide such a liquid metering device which is
operable when fully submerged within the liquid to be pumped.
Another object is to provide a liquid metering device which is
compact, has few moving parts, and is easily operated
automatically.
Other objects and advantages of the invention will become apparent
from the following detailed description and upon reference to the
accompanying drawings, in which:
FIG. 1 is a perspective view, partly cutaway, showing a liquid
metering device illustrative of the present invention disposed
within a typical liquid supply container or tank.
FIG. 2 is an elevational view of the illustrative liquid metering
device.
FIGS. 3 and 4 are elevational views, partly in section, showing
liquid unloaded (FIG. 3) and liquid fully loaded (FIG. 4) positions
of the illustrative liquid metering device.
FIG. 5 is a sectional view taken along the line 5--5 in FIG. 2.
FIG. 6 is a sectional view taken along the line 6--6 in FIG. 2.
FIG. 7 is an exploded, perspective view showing the component parts
of the illustrative liquid metering device.
While the invention will be described in connection with certain
preferred embodiments, it will be understood that it is not
intended to limit the invention to these particular embodiments. On
the contrary, it is intended to cover all alternatives,
modifications and equivalent arrangements as may be included within
the spirit and scope of the invention as defined by the appended
claims.
Turning now to the drawings, an illustrative liquid metering device
10 is shown in FIG. 1 disposed in a typical supply container or
tank 11 containing liquid to be metered and pumped to another
location. The fully enclosed type supply tank 11 shown has an
opening defined by a flange 12 in the top for receiving the liquid
metering device 10, and is provided with a liquid fill inlet 13
closed by a suitable cap.
As will be seen, the liquid metering device 10 includes a generally
cylindrically shaped pump assembly 14 mounted between rectangular
base and top plates 15 and 16, respectively, by means of vertical
supports 17 (four as shown). Also mounted between the plates 15 and
16, and located alongside the pump assembly 14, is a metering
assembly 18 which functions to adjustably set the volume of liquid
to be metered and pumped by the device 10.
The top plate 16 of the liquid metering device 10 is provided with
holes 16a for alignment with corresponding holes (not shown) in the
tank flange 12 and for receiving suitable fasteners (not shown) for
securing the metering device 10 within the tank 11. The plate 16
also includes holes 16b for receiving the upper ends of the
vertical mounting supports 17 and fasteners (not shown) therefore
(corresponding holes 15a are provided in the base plate 15 for the
lower ends of the supports 17).
For receiving a suitable pressurized gas (e.g. 25 psi. pressure),
such as air or an inert gas such as nitrogen, the top plate 16 is
provided with a gas inlet 19 having an on-off switch type valve 20.
The valve 20 includes a vent (not shown) for releasing the gas
pressure when desired (i.e. to discharge liquid from the pump when
it is loaded, as described below). The top plate 16 is also
provided with a liquid outlet 21 which directs the metered liquid
to its ultimate destination. Mounted above the top plate 16 is a
dial 22 associated with the metering assembly 18 to permit manual
adjustment of the pumping volume (as described in more detail
below).
Directing attention now to the pump assembly 14, as shown in the
drawings it includes a large cylindrical piston 23 disposed within
an outer cylindrical casing 24, and a small cylindrical piston 25
removably secured within a recess 26 provided in the center of the
large piston. The small piston 25 moves up and down within an inner
casing 27 which is secured to and extends part way down from the
top plate 16 into an annular space provided between the small
piston 25 and the recess 26 in which it is housed. The two pistons
23 and 25, which are secured together through a threaded connection
28, move up and down together at all times. In order to permit
alignment of the small piston 25 within its casing 27, the
connection 28 between the pistons 23 and 25 includes a wave washer
29a which produces spring tension between the two pistons, a lock
washer 29b, and an intermediate regular washer 29c. As shown, the
small piston 25, which may advantageously be formed of teflon or
similar corrosion resistant, low-friction material, presents a
round piston face 25a facing upwardly toward the top cover plate
16. Annular seals 25b are provided around the periphery of the
piston 25 to assure liquid-tight sealing engagement between the
piston and its casing 27.
Like the small piston 25, the large piston 23 also presents an
upwardly facing piston face 23a, in this instance annularly shaped
to fit between the outer 24 and inner 27 casings. Once more the
piston 23 may be formed of teflon or the like, and includes an
annular seal 23b held in place by a suitable seal retaining ring
23c.
To facilitate sliding movement of the pistons 23, 25 within their
respective casings 24, 27, it may be advantageous to construct the
casings of metal having an interior coating of low friction
material such as teflon or the like. Such a coating may also
desirably be resistant to corrosion by the liquid being pumped.
For urging the two pistons 23 and 25 normally upwardly and into an
unloaded (with liquid) position (see FIG. 3), a coil spring 30 is
located inside the lower portion of the outer casing 24 interposed
between tue bottom support plate 15 and the underside of the piston
23. The position of the coil spring 30 when fully compressed (see
description below) is shown in FIG. 4.
Communicating passages for the liquid passing through the liquid
metering device 10 are provided as follows. Liquid enters the
device 10 through a submerged suction inlet 31 provided in the
bottom of the base plate 15. The inlet 31 is covered by a
protective screen 32 supported between a shoulder 15b defining the
inlet 31 and a dished upper retaining cup member 33 against which
the coil spring 30 rests. Liquid entering the inlet 31 passes
upwardly into the underside of the dished member 33 and into a
flexible tubing 34, which may also be formed of teflon or the like.
The tubing 34 is suitably secured at one end to a central opening
33a provided in the dished member 33, and at the other end to an
internal channel 35 which runs longitudinally through the small
piston 25. As will be seen, the channel 35 communicates between the
flexible tubing 34 and an inner chamber 36 located adjacent the
operating face 25a of the small piston. The upper end of the
chamber 36 opens into the liquid outlet passage 21 provided in the
top plate 16. For preventing backward flow of liquid through the
pump, a pair of one-way (up and out only) check valves 37 and 38
are provided in the channel 35 and outlet 21, respectively.
Liquid flowing through the metering device 10 thus enters at the
inlet 31, passes through the screen 32 (to filter out any particles
of foreign matter that may be present), into the dished member 33
and thence through the tubing 34, the channel 35, check valve 37
and into the pumping chamber 36 from which it is ejected (as will
be described below) through the liquid outlet 21.
On the pressurized gas side of the device 10, gas entering through
the gas inlet 19 impinges on the piston face 23a and thereby forces
both pistons 23 and 25 downwardly against the bias of the coil
spring 30. As this occurs, the entering gas passes into and
occupies an annular chamber 39 formed between the inner 27 and
outer 24 casings. As the pistons 23 and 25 move downwardly, a
vacuum is created within the smaller chamber 36; this vacuum draws
the liquid upwardly from the tank 11 through the liquid inlet 31
and into the chamber 36 as previously described. When the entering
gas supply is terminated by shutting off the valve 20, the trapped
pressurized gases in the chamber 39 are vented through the valve
and the pistons 23 and 25 return to their upper position in
response to the urging of the coil spring 30.
For limiting the extent of downward movement of the unitary pistons
23, 25, the lower portion of the piston 23 carries a stop pin 40
(shown threaded into the piston body) which extends through a
vertical slot 24a provided in the casing 24 and is adapted to
cooperate with the metering assembly 18, as will now be described.
The assembly 18 includes a stepped drum 41 fixedly mounted by means
of a set screw 42 onto a vertical spindle 43 extending between a
collar 44 carried by the base plate 15 and an opening 16c provided
in the top plate 16. The upper end of the spindle 43 extends
through the opening 16c where the manually operable dial 22 is
affixed to it by means of a set screw 45. A seal ring 46 and
retaining collar 47 are fixed to the spindle 43 (by set screw 48)
just beneath the top plate 16.
Thus, the operator of the liquid metering device may adjust the
batch volume of liquid to be pumped by simply turning the dial 22
until the desired step 41a is located adjacent the casing slot 24a.
The downward stroke of the pistons 23, 25 then will continue only
until the stop 40 carried by the pistons engages the selected step
41a, at which time the pressurized gas valve 20 may be actuated to
release the gas pressure and thereby cause ejection of the measured
quantity of liquid from the chamber 36 into the outlet line 21. The
number and spacing of the steps 41a may be varied as desired to
provide the necessary liquid batch sizes for each particular
application. e
One of the features of the illustrative device resides in the
provision therein of means for preventing liquid leakage into the
pressurized gas chambers. To this end a porous washer 49,
preferably formed of teflon felt or like material, is provided
within the recess 26 at the base of the small piston 25. In the
event of liquid seepage past the piston seals 25b and into the
recess 26, the pressurized gas in the recess 26 forces such liquid
through the porous washer 49 and back into the tank 11.
Another feature of the illustrative arrangement resides in the
manner in which provision is made for the pistons 23, 25 to move
downwardly in the casing 24 and compress the spring 30, without at
the same time pinching or otherwise restricting flow of liquid
through the tubing 34. As will be seen from the drawings, the
tubing 34 is provided with a loose knot which, because of the
flexibility of the tubing, is capable of self loosening during
downward piston travel (see FIG. 4) and self-tightening during
upward piston travel (see FIG. 3). It has been found that pinching
of the tubing 34 is avoided if the mean slope of the knot is
arranged opposite to the spiral of the spring 30, as shown in the
drawings.
* * * * *