U.S. patent number 3,581,575 [Application Number 04/815,463] was granted by the patent office on 1971-06-01 for dispensing apparatus for receiving and discharging a precisely predetermined volume of fluid.
This patent grant is currently assigned to Fisons Limited. Invention is credited to Robert Roy Butler.
United States Patent |
3,581,575 |
Butler |
June 1, 1971 |
DISPENSING APPARATUS FOR RECEIVING AND DISCHARGING A PRECISELY
PREDETERMINED VOLUME OF FLUID
Abstract
A motorized syringe for receiving and dispensing and/or diluting
very accurately controlled amounts of liquids in combination with a
separate portable or remote, hollow-bodied control unit connected
by a flexible conduit to one or more such motorized syringes. The
operation of a plurality of the motorized syringes may be
integrated by means of a programmed operating means whose operation
cycle is initiated from the remote control unit connected
therewith, with the attendant advantage that complex operations
requiring the use of many such syringes in combination with one
another may be carried out at a single location, with the operator
merely exchanging vessels serving the liquid-conducting
outlet/inlet tube or tubes provided in the remote control unit and
connected with the flexible conduit, whereby the liquid is readily
dispensed or picked up; and, if necessary, some further stage of
the process can be initiated by actuation of one or more control
buttons provided on the control unit. The outlet/inlet tubes are of
relatively small diameters and have interchangeable probelike
portions with a free end projecting a substantial distance beyond
the body to facilitate picking up liquid from and/or dispensing
liquid into vessels having relatively narrow, elongated necks.
Inventors: |
Butler; Robert Roy (Tadworth,
Surrey, EN) |
Assignee: |
Fisons Limited (Felixtowe,
Suffold, EN)
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Family
ID: |
25217860 |
Appl.
No.: |
04/815,463 |
Filed: |
April 11, 1969 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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654737 |
Jul 1, 1967 |
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654737 |
Jul 20, 1967 |
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Foreign Application Priority Data
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Jul 26, 1966 [GB] |
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33589/66 |
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Current U.S.
Class: |
73/864.12;
73/864.18; 222/135; 222/144.5 |
Current CPC
Class: |
G01N
35/1067 (20130101); G01N 1/38 (20130101); G01N
2035/1069 (20130101) |
Current International
Class: |
G01N
1/38 (20060101); G01N 35/10 (20060101); G01n
017/00 () |
Field of
Search: |
;222/23,76,146,386,390,529,533,566,144.5,135 ;239/587,588,303--305
;248/68 ;285/137 ;141/21 ;78/425,425.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tollberg; Stanley H.
Assistant Examiner: Stack, Jr.; Norman L.
Parent Case Text
The present invention relates to a motorized syringe for dispensing
or diluting liquids in combination with a separate portable control
unit and is a continuation-in-part of my copending application Ser.
No. 657,737, filed July 20, 1967, abandoned.
Claims
I claim:
1. The combination of a control mechanism and pump means for
receiving and discharging a precisely predetermined volume of fluid
from associated fluid reservoir means to a delivery site, which
combination comprises:
a. pump means including first variable-volume displacement-chamber
pump means adapted for fluid flow communication with the reservoir
means;
b. an electrical motive power means operatively connected to and
for driving said pump means;
c. means including adjustable limit-stop means interconnected with
said pump means and motive power means providing for selectively
adjusting and effecting the precisely predetermined volumes of
fluid;
d. a hand-manipulatable housing of portable character capable of
being moved about a work area independently of the pump means, the
housing being provided with a fluid-conducting tubular probe having
one end projecting from the housing and with a fluid flow
communication line connecting the other end of the probe with the
pump means, said housing having at least one electrical switch and
related circuitry connecting it with the electrical motive means,
said switch being operable to selectively actuate the electrical
motive power means; and
e. a multiple-position valve means operatively connected with and
driven by said motive power means in synchronization with said pump
means and controlling the line of fluid flow communication to the
pump means, whereby in a first position the pump means is in fluid
flow communication with the fluid reservoir to provide intake of a
predetermined volume of fluid into the pump means, and in another
position to provide discharge of said fluid from the pump means via
said probe in the housing to a delivery site.
2. A combination as defined in claim 9 wherein the pump means
further includes a second variable-volume displacement-chamber pump
means operatively connected with said power means, and having means
providing fluid flow communication with said probe in the housing
for picking up into and discharging from the probe an independently
predetermined precise volume of fluid, said valve means including
means to provide fluid flow communication in a sequence of
positions not only between said first pump means and the associated
reservoir, and between said first pump means and said probe in the
housing, but also between said second pump means and said probe in
the housing, whereby in a desired sequence a precise predetermined
amount of first fluid is drawn into said first pump means, a
precise predetermined amount of a second fluid is drawn into said
probe by said second pump means, and subsequently the first and
second fluids are discharged through said probe.
3. An association of a combination as claimed in claim 1 with
another same combination also as claimed in claim 9, characterized
in that the said pump means and the said valve means of said
combinations serve one probe housing and in that there is further
provided a programmed operation means operatively connected with
said electrical motive power means and with said switch, said
programmed operating means having a cycle of operations initiated
by actuation of a switch in the housing, and which programmed
operating means thereby actuates the motive power means driving
each pump means and the valve means operatively serving the pump
means in the desired sequence.
4. An association as claimed in claim 3 wherein said one housing is
provided with a similar second probe and including fluid flow
communication lines similarly and separately connecting it
respectively with said pump means, reservoir means and said valve
means to selectively serve each of the related associations in the
combination
5. An association as claimed in claim 3 wherein the programmed
operating means is provided with switch-activated means for
effecting at least one interruption in the cycle of its operation
and the housing is provided with a corresponding number of
electrical switches operatively connected with said programmed
operating means so that subsequent switch actuation initiates a
further operation of the programmed operating means.
6. A combination as defined in claim 2 further including a
subcombination comprising:
1. a third variable-volume displacement-chamber pump means adapted
for fluid flow communication with a reservoir means;
2. an electrical motive power means operatively connected to and
for driving said third pump means;
3. means including adjustable stop means interconnected with the
said third pump means and the motive power means driving the third
pump means providing for selectively adjusting and effecting the
precisely determined volume of the displacement chamber of the
third pump means;
4. a multiple-position valve means operatively connected with and
driven by the motive power means driving the third pump means in
synchronization with the third pump means and controlling the line
of fluid flow communication to the third pump means, whereby in a
first position the third pump means is in fluid flow communication
with the reservoir means it serves to provide intake of a
predetermined volume of fluid into the third pump means, and in
another position to provide discharge to a delivery site of said
fluid from said third pump means via a probe in said housing to
which the third pump is connected by a fluid flow communication
line; and
further including a programmed operating means operatively
connected with the said electrical motive power means serving all
three pump means and said switch in the housing, said programmed
operating means having a cycle of operations initiated by actuation
of said switch in the housing and with programmed operating means
thereby actuates the motive power means driving each pump means and
the valve means operatively serving the pump means in desired
sequence.
7. A combination and subcombination as claimed in claim 6 wherein
the reservoir means connected to the third pump means is separate
from the reservoir means connected to the first pump means; the
electrical motive power means driving the third pump means is
separate from that driving the first and second pump means; the
fluid-conducting probe connected to the third pump means is
separate from the probe serving the first and second pump means;
and the multiple-position valve means serving the third pump means
is separate from the multiple-position valve means serving the
first and second pump means.
8. A combination as defined in claim 1 further including a
subcombination comprising:
1. a third variable-volume displacement-chamber pump means adapted
for fluid flow communication with a reservoir means;
2. a second fluid-conducting tubular probe in the said
hand-manipulatable housing having one end projecting from the
housing and with a fluid flow communication line connecting the
other end of the probe with the third pump means;
3. a fourth variable-displacement-chamber pump means in fluid flow
communication with said second probe in said housing for picking up
into and discharging from the second probe an independently
predetermined precise volume of fluid;
4. an electrical motive power means operatively connected to and
for driving said third and fourth power means;
5. means including adjustable stop means interconnected with the
said third and fourth pump means and the motive power means driving
said third and fourth pump means providing for independently and
selectively adjusting and effecting the precisely predetermined
volumes of the displacement chambers of said third and fourth pump
means;
6. a multiple-position valve means operatively connected with and
driven by the motive power means driving the third and fourth pump
means in synchronization with the third and fourth pump means and
controlling the lines of fluid flow communication to the third and
fourth pump means to provide fluid flow communication in a sequence
of positions between the third pump means and the reservoir means
which it serves, between the third pump means and the second probe
and between the fourth pump means and the second probe whereby in a
desired sequence a precise predetermined amount of a fluid is drawn
into the third pump means, a precise predetermined amount of
another fluid is drawn into the second probe by the fourth pump
means, and subsequently the two fluids are discharged through the
second probe; and
further including a programmed operating means operatively
connected with the electrical motive power means serving the four
pump means and a switch in the housing, said programmed operating
means having a cycle of operations initiated by the actuation of
the switch in the housing and which programmed operating means
thereby actuates the motive power means driving each pump means and
the valve means operatively serving the pump means in the desired
sequence.
9. The combination and subcombination as claimed in claim 8 wherein
the reservoir means connected to the third pump means is separate
from the reservoir means connected to the first pump means; the
electrical motive power means driving the third and fourth pump
means is separate from that driving the first and second pump
means; and the multiple-position valve means serving the third and
fourth pump means is separate from the multiple-position valve
means serving the first and second pump means.
10. The combination and subcombination as claimed in claim 9
wherein the first and second probes in the hand-manipulatable
housing are moveable from a splayed-apart position to a closer
adjacent position by means including a slidable member slidable
along the probes to control the relative positions of the free ends
of the probes.
11. An association as claimed in claim 6 wherein the programmed
operating means is provided with switch-activated means for
effecting at least one interruption in the cycle of its operation
and the housing is provided with a corresponding number of
electrical switches operatively connected with said programmed
operating means so that subsequent switch actuation initiates a
further operation of the programmed operating means.
12. An association as claimed in claim 8 wherein the programmed
operating means is provided with switch-activated means for
effecting at least one interruption in the cycle of its operation
and the housing is provided with a corresponding number of
electrical switches operatively connected with said programmed
operating means so that subsequent switch actuation initiates a
further operation of the programmed operating means.
Description
Motor driven syringes, which comprise a hollow cylinder having a
plunger reciprocated therein so as to pick up and discharge liquid,
find use in such laboratory operations as the dispensing of
accurately controlled amounts of liquid and the picking up and
dispensing of samples of liquid for test purposes. Motorized
syringes have the advantages over pipettes and manually operated
syringes whereby consistently reproducible accurate results may be
obtained and that the operator is freed from the need to use one or
both hands to operate the pipette or syringe. However, it has been
necessary to actuate the electrical or like control mechanism for
the motorized syringe and this has hitherto formed an integral part
of the housing within which the motorized syringe has been mounted.
This, coupled with the fact that the motorized syringe and
associated mechanism are comparatively bulky objects, has meant
that an operator has had to bring the vessel whose liquid is to be
sampled or which is to receive liquid to the motorized syringe.
This results in excessive movement around a work area. Furthermore,
where liquid in a vessel was to be subjected to a series of
samplings, additions or dilutions, it has been necessary to
transfer the vessel from one place to another in order that the
vessel could be located at each of the motorized syringes required
to carry out the overall operation. Where the overall operation was
complex in nature this would require a considerable bank of
syringes each one of which had to be visited and actuated in the
correct sequence, often with exchange of liquid receptacle during
the operation. Thus such an arrangement was cumbersome in structure
and operation, and also lent itself readily to human errors in view
of the complexity of its operation.
We have now devised a remote control unit for use with one or more
motorized syringes which overcomes the need to take vessels to the
motorized syringe and which, because the control of the syringes is
located at one place (and not upon each syringe as before) makes it
possible to integrate the operation of a plurality of syringes by
means of a programmed operating means whose operation cycle is
initiated from the remote control unit. This has the advantage that
complex operations requiring the use of many syringes in
combination with one another may be carried out at a single
location, the operator merely exchanging vessels serving the liquid
inlet/outlet pipe or pipes in the control unit whereby the liquid
is dispensed or picked up and, if necessary, initiating some
further stage in the process by actuation of a button of the
control unit.
Accordingly, the present invention provides the combination of a
control mechanism and one or more motorized syringes each adapted
to receive and discharge accurately controlled amounts of liquid
and provided with one or more inlet/outlet pipes, which syringes
are adapted to be operated by the actuation of one or more
electrical switches, characterized in that the control mechanism is
a remote control unit comprising a housing adapted to be held in
the hand and to be moved about a work area independently of the
motorized syringe or syringes, which housing is provided with one
or more electric switches adapted to actuate the motorized syringe
or syringes and with one or more conduits adapted to permit the
flow of liquid through the housing and which are adapted to be
connected to the motorized syringe or syringes by flexible
conduits.
From a preferred aspect, the invention provides a combination as
described above wherein two or more motorized syringes are caused
to act in combination by a programmed operating means whose cycle
of operations is initiated by actuation of a switch in the control
unit.
The motorized syringes for present use comprise an accurately
machined cylinder within which a close-fitting plunger is
journaled. The cylinder and plunger may be made from any suitable
materials such as glass, nylon, stainless steel and the like and
suitable cylinders and plungers are commercially available. The
plunger may be provided with a sealing member, such as an O-ring,
to ensure sealing contact between the plunger and the cylinder
walls. The plunger is reciprocated within the cylinder by means of
a motor-driven ram or the like. For example the free end of the
plunger may be carried by a motor-driven carriage, the cylinder
being held stationary or vice versa. While the cylinder and plunger
may be exchanged with others in order to provide variation in the
amount of liquid picked up and discharged during a full stroke of
the plunger within the cylinder, it is usually more convenient to
provide the syringe-driving mechanism with adjustable stops which
may be used to alter the length of the stroke of the plunger in the
cylinder. These stops may take the form of buffers which prevent
further movement of the plunger where the linkage between the
plunger and its driving means is provided with a clutch, such as a
slipping spring clutch, which permits slip or relative movement.
Alternatively, the stops may actuate switches which stop and may
reverse the motion of the plunger.
The outlet from the syringe may be connected directly with the
control unit where the syringe is to pick up and discharge liquid
only through the control unit. However it will usually be preferred
to provide the syringe with a valving means, for example a twist
valve, which operates in harmony with the stroke of the plunger to
ensure that, where the plunger has draw liquid into the cylinder,
the cylinder may be sealed to prevent drainage of liquid therefrom
or from the liquid source. Where the syringe is to pick up liquid
from a separate supply and to discharge it through the control
unit, as is the case where the syringe is to dispense a reagent or
diluent, the valve means may be provided with the requisite number
of inlets and outlets to which the source of liquid supply and the
control unit may be connected. The use of a twist valve is
particularly preferred for the valving means since the residual
liquid held in a twist valve after operation is small, minimizing
the risk of contamination of successive liquids which pass
therethrough. Furthermore a twist valve suffers less than other
forms of valve from jamming.
The plunger and valving means may be driven by any suitable motor
and linkage system and the one motor may drive both the plunger and
the valve. It is preferred to use a synchronous reverse-phase
electric motor. The necessary circuitry to ensure the correct
sequence of operations of the plunger and valve may be varied to
suit any particular operational sequence and are conventional in
nature.
As indicated, a single motorized syringe may pick up liquid from
some source and this may not be via the control unit, and then
discharge the liquid via the control unit. Such a syringe may
therefore be used to dispense a given amount of diluent or reagent
into a vessel or to transfer a given amount of sample liquid from
one vessel to another. For convenience, such a form of motorized
syringe and its associated mechanism will be denoted herein as a
dispenser. However, where it is desired to pick up a sample of
liquid and then to discharge it with a diluent, it will be
appreciated that two syringes may be required. These syringes may
be operated separately or, more preferably, may be operated in
unison by a single motor. In the latter case, one motorized syringe
may be of the form described above for a diluter, the other may be
of the same construction but of different capacity and provided
with valving means whereby it picks up and discharges liquid only
via the control unit. Where the second syringe has a different
length of stroke from the other, its plunger may be driven by means
of a magnetic clutch from the driving means of the other syringe
which permits relative movement between the two plungers once one
has completed its stroke. Such a two-syringe apparatus will be
denoted herein as a diluter. Motorized syringes of the described
type as used in dispensing and diluting systems are commercially
available, for example, through Fisons Scientific Apparatus, Ltd.,
Loughborough Leicestershire, England.
It will be appreciated that where a syringe is to pick up and
discharge a series of samples of different liquids, it is
undesirable that contamination of one sample by another should
occur. It is therefore preferred that sample liquid should not be
drawn up into the cylinder of the syringe since this is difficult
to clean effectively between each sampling. It is especially
preferred that liquids to be sampled should be accommodated in the
conduit in the control unit which they serve. The samples may be
picked up and ejected without contaminating the syringe, whose
cylinder is full of air or a liquid, such as a diluent, which does
not contaminate successive samples or other liquids which are to
pass through the conduit. The conduit may be washed clean by
passing diluent through it, which also discharges the sample, or by
some other means. The air or liquid in the cylinder of the syringe
serves as a piston to transmit the suction or expulsion forces
generated in the syringe to the liquid to be sampled.
The control unit for present use comprises a housing which is to be
held in the hand and which is provided with one or more tubes or
like conduits through which liquid may flow to and from the
appropriate motorized syringe or syringes and with one or more
electrical switches whose actuation initiates the operation of a
given syringe or series of syringes. The housing may be of a pistol
grip type or may be an elongated cylindrical or cigar shape. It may
be made from any suitable material such as a chemically resistant
synthetic resin, e.g. nylon, polyethylene, polystyrene, or the
like.
The tubes or like conduits with which the housing is provided may
be mounted externally, or more preferably, are encased within the
housing. These tubes are provided at one end with means for
connecting them to a flexible conduit or tube which permits the
flow of liquid between the control unit and the dispenser and/or
diluter mechanisms which it serves. Such connections may be by
means of a screw union, a bayonet or push fit. The other ends of
the tubes of the control unit protrude sufficiently far from the
housing to enable liquid to be picked up from and dispensed with
directional accuracy into the comparatively elongated and
narrow-necked vessels such as test tubes used in laboratories. For
a tube which is to be used solely for dispensing liquids, the
extent of protrusion need only be sufficient to ensure that
accurate directional control is achieved and the protruding portion
or probe may be from, say, 3 to 6 inches long. However, the bore of
a discharge tube may be related to the capacity of the syringe
which it serves. Thus for a 20-ml.-capacity syringe the protruding
portion of the tube in the control unit is preferably about 1.5 mm.
in internal diameter and for 10 ml. and 5 ml. syringes the internal
diameters are about 1.0 mm. and 0.5 mm. respectively. For a tube
which is to be used for the sampling of liquids it is usually
preferred that the capacity of the tube be such that little or none
of the sample enters the motorized syringe which the tube serves.
It is also preferred that, where a control unit is provided with
both discharge and a sampling tube, the sampling tube protrude from
about one-half an inch to 1 inch further than the discharge tube.
The appropriate dimension of the protruding portions or probes for
each tube or like conduit in the control unit may be readily
assessed for any given case.
The probes or protruding portions of the tubes in the control unit
are preferably made detachable, for example by a screw, bayonet or
push fit, to permit interchange for different syringes and
different operations. The probes and associated tube in the control
unit may be made from any suitable chemically resistant material
such as polyethylene or stainless steel.
The number of tubes or like conduits with which the control unit is
provided may be dependent upon the number and the natures of the
syringes which it is to control. While a liquid sample may be
picked up and discharged through the same tube and probe and while
a diluent for the sample may also be discharged through the same
tube and probe, it will usually be necessary to provide a separate
tube and probe in the control unit for each liquid to be passed
through the handset, especially where successive liquids might
interact. For convenience it is preferred to provide a standard
type of control unit having, say two tubes which may be provided
with a range of interchangeable probes. Where an operation makes
use of more liquids than can be handled by one control unit without
contamination, additional control units may be used. It is also
usually preferred that each tube and probe in the control unit
serve only one dispenser and/or diluter; although where mixing of
liquids in the one tube and probe is not deleterious, several
diluters and/or dispensers may be served by the one tube and probe
via a manifold.
While the probes which may be fitted to control unit are usually
straight stainless steel tubes of varying dimensions, we have found
it convenient to provide a control unit, wherein two tubes are to
be used for the simultaneous pickup of samples from a common
source, with a pair of probes of flexible construction which is
provided with means for altering the relative positions of the free
ends of the probes. For example the probes may be a pair of
diverging tubes having a slideable collar encircling them both
which may be slid down the probes to bring their tips together for
simultaneous sampling from one vessel then be slid up the probes to
permit them to splay and discharge the samples into two separate
vessels.
As indicated above, the housing of the control unit is also
provided with one or more electrical switches, which are preferably
of the push button type, for initiating the operation of the
syringe or syringes which the control unit serves. The switch may
be connected to the syringe mechanism or to the programmed
operating means therefor in the conventional manner. While the
control unit may be provided with an individual switch to actuate
each syringe which it serves, it is preferred to provide the
control unit with only one switch. Where one syringe or a diluter
mechanism is served by the control unit, the switch on the control
unit may be connected directly to the syringe mechanism. However,
where a plurality of syringes are served which operate in
cooperation with one another, the switch on the control unit may be
connected to a programmed operating means which operates the
syringes in the desired sequence and which is itself actuated by
the switch on the control unit. The programmed control means may
take the form of a rotating disc adapted to trip switches operating
the syringes or may take the form of a series of relays. While the
programmed operating means may be one which will carry out the
whole of the intended test operation upon a single actuation of the
switch on the control unit, it is usually preferred that the
program be designed to carry out the overall operation in a number
of stages, each of which requires initiation from the control unit.
Such interrupted process enables the operator to identify with the
ease the stage of the process which has been reached and to change
vessels or to incubate a sample during one of the interruptions if
required. If desired, the programmed operating means may be so
designed that, once any particular stage is initiated, actuation of
the switch on the control unit will have no effect until the stage
has been completed.
The circuitry required for a programmed operating means may be
readily devised for any given operation.
In addition to the switches and the conduits, the control unit may
also be provided with one or more indicator lamps which serve to
show an operator which stage of an overall operation has been
reached. The number of lamps required may be varied from operation
to operation but will rarely exceed three. The lamps and their
circuitry are conventional in nature.
The control unit is connected to dispensers and/or diluters it
serves or the programmed operating means therefor by flexible
electrical leads and liquid conduits. The flexible conduits may
take the form of tubes made from a synthetic resin such as
polyethylene or tetrafluoroethylene. The conduits and leads may be
housed together in a common covering or sheath.
While the use of a remote control unit provides many advantages
where a single dispenser or diluter is used, it is of especial
benefit when combined with the use of a programmed operating means
to control a plurality of dispensers and diluters. The devices of
the invention may find use for example in testing for blood glucose
or urea, in preparing double samples of different concentrations
for the testing of the sodium and potassium content of the sample
in a flamephotometer and in preparing samples for hemoglobin or
leucocyte counts.
By way of example the invention will be illustrated by a
double-dilution device in which samples of different concentrations
are prepared from a single source and with respect to the
accompanying drawings in which:
FIG. 1 is a schematic representation of the apparatus employed;
FIG. 2 is a plan view of a diluter mechanism;
FIG. 3 is a vertical section of the control unit;
FIG. 4 is an enlarge vertical section showing the probes for the
control unit of FIG. 3,
FIG. 5 (identified as FIG 5a and FIG. 5b on two pages) is the
circuit diagram of the apparatus in which the component parts are
denoted by the standard form of symbol and identification;
FIGS. 6 and 7 are schematic representations of the most simplified
form of a dispenser and diluter mechanism, respectively, with other
basic components comprising the basic inventive combinations
defined in respectively the first two claims;
FIG. 8 is a similar simplified schematic diagram of the combination
systems utilizing two dispenser mechanisms, and as defined in the
third claim;
FIG. 9 is a further simplified schematic representative of a
combination embodying one dispenser mechanism and one diluter
mechanism feeding one or two probes; and
FIG. 10 is still another schematic representation of two diluter
mechanisms with two probes, which is an even more simplified
representation of FIG. 1.
The apparatus for the double dilution comprises a sample in a
beaker or like vessel 1, a control unit 2 having a double flexible
probe 3, one probe being connected by flexible polythene tubing 10
to a diluter mechanism 4, the other probe to another diluter 5 by
tubing 10a. The control unit is provided with a pushbutton
electrical switch 6 which is connected to the interlink or
programmed operating means 7 which causes the two diluters to
operate in unison upon actuation of switch 6. Each diluter is
connected to a reservoir or supply of water which is used as the
diluent. The power for the interlink and the diluters is supplied
by a 24 -volt transformer (not shown).
Diluter 4 shown in FIG. 2 contains two motorized syringes 8 and 9,
syringe 8 picks up the sample to be diluted by suction via line 10
and syringe 9 picks up water from the supply or reservoir R, both
syringes discharge their contents down line 10 to the control unit
and out via one arm of the double probe 3. Both syringes are fitted
into a P.T.F.E./stainless steel twist valve 11 which is operated
through the crank 12 and the connecting rod 13 by a synchronous
reverse-phase motor (not shown in FIG. 2, but shown schematically
at M in FIGS. 6--10). This valve connects syringe 8 with control
unit and syringe 9 in turn with the supply of water and then with
the control unit for the pickup and discharge stroke of the plunger
in syringe 9 respectively. The motor which drives valve 11 also
drives a rack 14 on which is mounted a bracket 15 which engages
with the free end 16 of the plunger in syringe 9. The barrel of
syringe 9 is held firmly against valve 11 by means of an L-shaped
clamp 17. The barrel of syringe 8 is held against the valve 11 by a
plastic clamp 18 which can be tightened by moving it along a
support rod 19. The free end 20 of the plunger of syringe 8 is held
in a second plastic clamp 21 which also slides along support rod 19
with additional support from the guide rod 22 which is mounted
under support rod 19. The clamp 21 carries a magnet 23 which makes
contact with an adjustable catchplate 24 mounted on bracket 15.
The volume picked up and delivered by syringe 9 is controlled by
two adjustable stops 25 and 26 which can be move to and fro along
actuating rod 27 which is mounted along side the rack 14. Fitted to
the bracket 15 are two knurled wheels 28 and 29 which act as trip
levers for the stops. When one of the knurled wheels strikes a
stop, the actuating rod is moved thus actuating microswitch 30 to
which it is connected and causing the motor to stop and reverse.
The volume picked up by syringe 8 is controlled independently by
another adjustable stop 31 mounted on the guide rod 22. When clamp
21 strikes the stop 31, the adjustable catchplate 24 parts from the
magnet 23 and the plunger in syringe 8 is not longer driven.
In operation, both plungers are initially at the end of their
forward strokes and syringes 8 and 9 are empty. Valve 11 connects
syringe 8 with the control unit and syringe 9 with the supply of
diluent. Upon initiation of the dilution operation, the motor in
the diluter is energized and draws the bracket 15 away from the
valve 11. This commences the suction stroke for the syringe 9 which
continues until stop 26 is tripped by knurled wheel 29 which occurs
at the point at which the syringe has picked up the desired
quantity of diluent. During the movement of bracket 15, catchplate
24 carries magnet 23 with it and hence also draws the plunger for
syringe 8 with it. When clamp 21 strikes the stop 31 further travel
of the clamp is prevented, the contact between the catchplate 24
and the magnet is broken and the suction stroke of the plunger in
syringe 8 is complete even though the suction stroke of syringe 9
may continue.
When stop 26 is tripped by knurled wheel 29 at the end of the
suction stroke of syringe 9, the motor is stopped and reversed by
microswitch 30 and valve 11 is turned to form a common discharge
patch from both syringes via line 10 to the control unit. If
desired, the turning of the valve may take place with an
intermediate closed position to minimize the risk of backflow.
Where the valve turning is carried out in a series of steps with an
intermediate closed position, further actuation of the button on
the control unit may be required to turn the valve from its closed
position to that at which it provides the common discharge path for
syringes 8 and 9.
When the valve 11 is in the discharge position, the motor drives
rack 14 towards the valve 11 on the discharge stroke of syringe 9.
As the rack advances, catchplate 24 recontacts magnet 23 and the
plunger of syringe 8 is caused to carry out its discharge stroke in
unison with the rest of the discharge stroke of syringe 9.
Discharge of the syringes continues until knurled wheel 28 strikes
stop 25 at the end of the travel of the plunger in syringe 9. The
motor drive is disconnected from rack 14 and valve 11 is turned to
connect syringe 9 with the supply of diluent or to an intermediate
closed position and the diluter is ready to repeat its operation
upon further actuation of switch 6 in the control unit.
As indicated above, the plunger of syringe 8 does not actually draw
the liquid to be sampled into the cylinder of the syringe but only
into that arm of probe 3 which it serves by means of the suction
generated in line 10.
The syringes 8 and 9 may be made from nylon, glass or other
suitable noncorrodible materials and other parts may be made from
for example, stainless steel.
The second diluter 5 is of similar construction as diluter 4 except
that the capacities of syringe 8 and/or 9 may be different in order
that a different in order that a different proportion of sample and
diluent is discharged from diluter 5.
The two diluters are caused to act in unison upon actuation of the
single button in the control unit by means of the interlink 7 which
comprises a series of relays the first of which is actuated by the
switch 6 and itself actuates a series of further relays in the
desired sequence. The function and construction of the interlink
will be readily appreciated from the circuit diagram FIG. 5. It is
preferred to construct the interlink 7 of a size suitable for
mounting upon one end of either of the diluters 4 or 5 to form a
single unit as shown in FIG. 1.
Controlling the operation of diluters 4 and 5 and interlink 7 is
control unit 2 shown in FIG. 3. This comprises a hollow
cigar-shaped housing made from nylon. This housing is provided with
the pushbutton switch which closes contacts 32 and 33 between the
electrical leads a and a.sup.1 which are connected to the interlink
7 to energize the relays in interlink 7.
The housing is also provided with a pair of polyethylene tubes 34
encased within the housing. One tube is connected to the valve 11
on one diluter, the other tube to the valve on the other, by means
of the flexible lines 10 and 10a referred to above. The free ends
of each of tubes 34 are provided with flexible stainless steel
probes 35 and 36 in a push fit. As may be seen from FIG. 4, each
probe is of stepped shape and both are encircled by a collar 37
which may be slid over the stepped portion of the probes to urge
their tips together or slid off the stepped portion to permit the
probes to splay apart. The splayed position (shown by full lines in
FIG. 4) permits simultaneous discharge from diluters 4 and 5 to two
different vessels, the closed position (shown in dotted lines)
permits the simultaneous pickup of samples by diluters 4 and 5 from
the one vessel.
The housing is also provided with two indicator lamps, one of which
is shown diagrammatically as 38 in FIG. 3. This lamp is a
conventional indicator lamp and is connected by leads b and b.sup.1
to the interlink 7 and serves to show an operator the point in the
overall position which has been reached.
The leads for the switch and the indicator lamps are housed with
the flexible tubes connecting the control unit to the diluters in a
common sheath 39.
In carrying out a double dilution using the above apparatus, the
diluters initially have all syringes empty and ready to commence
their suction strokes. The bottom of the two indicator lamps on the
control unit is on. The operator slides collar 37 over the step of
probes 35 and 36 to bring their tips together and inserts the
probes into the liquid to be sampled. Button 6 is actuated which
actuates the interlink 7 which energizes the motors on diluters 4
and 5 to drive the plungers for all syringes on their suction
strokes. Liquid sample is drawn into probes 35 and 36 and diluent
is picked up by syringes 9 in each diluter. During this operation
neither indicator lamp 38 is on, but the top light goes on when
both of syringes 9 have completed their suction stroke, stops 26
have been tripped by knurled wheels 29 and microswitches 30 have
reversed the motors and turned the valves 11, in this case to an
intermediate closed position. The diluters are now ready to
discharge the diluent and samples. Interlink 7 is programmed so
that further operation of the diluters requires further actuation
of the button 6 at this point. The operator removes the probes from
the sample vessel, slides collar 37 off the step of the probes to
permit them to splay apart and inserts the probes into two separate
fresh receiving vessels before actuating button 6. The diluters
then discharge their contents into the two vessels to provide two
samples of different concentration. During the discharge the top
lamp 38 is on. At the end of the discharge, diluters 4 and 5 and
interlink 7 automatically revert to their starting positions in
readiness for another dilution operation and the bottom indicator
light only is switched on.
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