U.S. patent number 3,683,977 [Application Number 05/037,500] was granted by the patent office on 1972-08-15 for liquid dispensing apparatus.
This patent grant is currently assigned to Beckman Instruments, Limited. Invention is credited to James A. Crowe, Willi Krattenmacher.
United States Patent |
3,683,977 |
Crowe , et al. |
August 15, 1972 |
LIQUID DISPENSING APPARATUS
Abstract
There is disclosed a liquid-dispensing apparatus including a
support, a position-adjustable head mounted on said support and
adapted to carry in a depending position a plurality of syringes,
having reciprocal pistons. The head is motor driven for raising and
lowering the syringe needles into and out of containers for taking
in and dispensing fluids therefrom. A precision ground rack and
pawl arrangement is provided for predetermining the amounts of
fluid dispensed from the syringes. A tray transport is provided for
moving a plurality of rows of containers beneath the syringes. A
control circuit provides for either manual or automatic operation
of the system.
Inventors: |
Crowe; James A. (Glenrothes,
EN), Krattenmacher; Willi (Geneva, CH) |
Assignee: |
Beckman Instruments, Limited
(Glenrothes, GB)
|
Family
ID: |
10233584 |
Appl.
No.: |
05/037,500 |
Filed: |
May 15, 1970 |
Foreign Application Priority Data
|
|
|
|
|
May 21, 1969 [GB] |
|
|
25,804/69 |
|
Current U.S.
Class: |
141/130; 74/1.5;
141/181; 141/183; 141/167; 141/242 |
Current CPC
Class: |
G01N
1/18 (20130101); G01N 1/38 (20130101); G01N
35/1016 (20130101); Y10T 74/1502 (20150115); G01N
35/1065 (20130101) |
Current International
Class: |
G01N
1/38 (20060101); G01N 1/18 (20060101); G01N
35/10 (20060101); B65b 003/12 () |
Field of
Search: |
;73/423A,425.6 ;74/1.5
;141/129,130,167,177-179,181-185,190,191,242 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Earls; Edward J.
Claims
What is claimed is:
1. A liquid dispensing apparatus comprising:
a support means;
a movable head mounted on said support means;
means, including a head drive motor, connected to said head and
said support means for raising and lowering said head in a
substantially vertical direction relative to said support;
at least one syringe mounted on said head, said syringe having a
movable piston therein for drawing fluid into and discharging fluid
from said syringe;
filling and discharge means mounted on said head and coupled to
said movable piston for moving said piston to fill and discharge
said syringe;
a movable arm mounted on said support and adapted to carry a
plurality of rows of containers, said arm being movable
substantially horizontally and arranged to move said plurality of
rows of containers successively beneath said syringe to receive
liquid dispensed from said syringe;
indexing means for controlling the position of said movable arm
whereby selected rows of containers may be presented sequentially
beneath said syringe;
indexing drive means for actuating said indexing means for
controlling the position of said movable arm;
control means coupled to said filling and discharge means for
dispensing predetermined quantities of fluid from said syringe;
electric circuit means intercoupling said head drive motor, said
indexing drive means and said control means for sequentially
positioning a selected row of containers beneath said syringe,
lowering said head, discharging a predetermined quantity of fluid
from said syringe, raising said head and initiating a new sequence;
and
said electric circuit means further includes means for varying the
quantity of fluid dispensed from row to row of said containers.
2. A liquid dispensing apparatus of claim 1 wherein said electric
circuit means further includes adjustable switch means for
selectively adjusting the lower limit of travel of said head.
3. A liquid dispensing apparatus according to claim 1 further
including manually actuated means associated with said electric
circuit means for raising and lowering said head, actuating said
indexing means and operating said control means independently of
said sequence.
4. A liquid dispensing apparatus according to claim 1 further
including a plurality of syringes arranged in a row on said
head.
5. A liquid dispensing apparatus according to claim 4 wherein said
plurality of syringes are mounted on a syringe carrying frame
detachably secured to said head.
Description
This invention relates generally to liquid-dispensing apparatus and
more particularly to liquid-dispensing apparatus which may withdraw
a quantity of sample from a plurality of containers and dispense
into successive containers precise amounts of the sample.
In both clinical and industrial processes there is a need to break
a given sample down into precisely known quantities for further
testing. Further, various processes require the addition of various
reagents to a plurality of samples. When large numbers of samples
are being processed, the handling and processing is both time
consuming and tedious.
There is a need in both clinical and industrial laboratories for
automatic apparatus to handle large numbers of sample which may be
used not only to break the various samples down into smaller, known
quantities for further processing but may also be utilized as a
reagent addition apparatus. The present invention fulfills this
need.
The liquid-dispensing apparatus disclosed herein may be used, after
appropriate set-up, to break down a plurality of samples in to
various known smaller quantities. The apparatus may be programmed
to dispense differing quantities into different rows of containers.
The apparatus may also be utilized to automatically dispense a
given quantity of reagent or reagents into successive rows of
containers, the quantity so dispensed being variable from row to
row.
An embodiment of the present invention will now be described by way
of example, with reference to the accompanying drawings in
which:
FIG. 1 shows the syringe-containing head of the apparatus for
dispensing liquid into a container according to the present
invention;
FIG. 2 is a detail of a portion of the apparatus of FIG. 1;
FIG. 3 shows the brake for the head;
FIG. 4 is a view of a detail of the head showing the rack and pawl
arrangement which permits predetermined quantities of liquid to be
dispensed from the apparatus;
FIG. 5 is a detail of FIG. 4 shown to a larger scale;
FIG. 6 shows the indexing bar of the apparatus and its associated
microswitches;
FIGS. 7a and 7b together are an electrical diagram of the control
system for the apparatus;
FIG. 7A shows a motor control circuit and motor winding connections
which are part of the control system illustrated in FIGS. 7a and
7b, and FIG. 7B is a bar graph showing the relationship between the
operating cycles of certain switch contacts in such control system;
and
FIGS. 8 and 8A show the arrangement of the dispensing needle and a
container in the form of a test tube.
In the drawings, there is shown liquid-dispensing apparatus for
sequentially dispensing predetermined quantities of liquid from a
plurality of syringes 10, arranged in a row and mounted in a
depending manner on head 20, into a plurality of rows of containers
which may be in the form of test tubes 11 as shown in FIGS. 8 and
8A.
As shown in FIG. 1 and FIG. 2, the head 20 is mounted on two
laterally-spaced slideway guides 23 which are inclined at a small
angle to the vertical so that the head 20 is movable in an
approximately vertical plane between upper and lower limits by an
electric motor 21 which drives a crank mechanism 22, one end of
which is pivotally connected to the head 20. Coil springs 20A shown
in FIG. 1 are arranged to counterbalance the weight of the head 20,
and when the motor 21 is de-energized the head 20 is secured in
position by a caliper brake 25, shown in FIG. 3 which grips an
elongate bar 25A secured to the head 20.
Referring now to FIGS. 1 and 4 each of the syringes 10 has a hollow
body 13, a piston reciprocally movable therein, and a hollow needle
12 projecting therefrom. The needle 12 may be made of plastics
material such as polythene, polypropylene, or polyethylene, and
each body 13 is fixedly secured to a replaceable frame 13A which is
releasably secured to the head 20 by thumb screws 14.
Rods 15 connected to the pistons project from the syringes 10 and
are attached to a common crossbar 16 from opposite extremities of
which depends a precision-ground rack 17.
A motor-driven spring-loaded pawl 18 is arranged for selective
engagement with the teeth of the rack 17 whereby the crossbar 16
and hence each of the syringe pistons may be moved downwardly
relative to the head 20, in the direction of the arrow A in FIG. 4,
by a predetermined amount so as to cause each of the needles 12 to
dispense a predetermined quantity of liquid from the syringe
10.
A handle 16A is secured to the crossbar 16 and the pawl 18 is
spring-loaded so that the crossbar 16 may be moved upwardly by hand
in order to fill each of the syringes 10 with liquid to be
dispensed and, as is best shown in FIG. 5, the pawl 18 is pivotally
mounted on a block 30 which in turn is mounted on the head 20 for
pivotal movement about a horizontal axis 31 by means of an arm 32
attached to a follower 33 which is driven by a motorized cam 34
mounted on the shaft of a dispenser motor 90 (FIG. 7b) as will be
described hereinafter.
The arrangement of the ratchet 17 and the pawl 18 is such that when
the cam 34 is rotated through one revolution the ratchet 17 is
driven downwardly by approximately one tooth pitch, which
represents 25 microliters of liquid dispensed from the needle 12,
and, at the end of the downward movement, the pawl 18 remains
locked between the teeth of the ratchet 17 so that overtravel of
the syringe pistons is prevented.
An adjustable stop 35 mounted on the head 20 is provided to limit
the downward travel of the pawl 18 and adjustment of the stop 35
varies the quantity of liquid dispensed from the needle 12.
In order sequentially to dispense liquid from the syringes 10 into
the test tubes 11, the tubes 11 are arranged in a matrix formation
on a movable dispenser tray 36 (shown only in FIG. 1) so that each
of the ten syringes 10 may simultaneously dispense liquid into a
first row of ten tubes 11, whereafter the tray is moved or indexed
through the dispenser to present a second row of ten empty tubes 11
into which the syringes 10 may again dispense liquid. This process
may be repeated for any desired number of times within the
liquid-containing capabilities of the syringes 10, but in the
apparatus described herein there are twelve rows of tubes 11.
The dispenser tray 36 is mounted on an arm 40 which is mounted on
slideways 40A (only one being shown) for movement through the
dispenser apparatus in a direction approximately normal to that in
which the head 20 is movable. The arm 40 is biased in one direction
by a spring (shown schematically at 38) and is maintained in a
selected position by a spring-loaded pawl 41 upstanding from the
arm 40, as shown in FIG. 6, which engages one of the twelve pins 42
radially upstanding from an indexing bar 43. The bar 43 is
rotatable by a crank mechanism 43A driven by an electric motor 75,
FIG. 1, and the pins 42 are axially spaced-apart and
circumferentially spaced from one another by 30.degree. so that
when the bar 43 is rotated through 30.degree. (i.e. one twelfth of
a revolution) the arm 40 is moved or indexed forwards by one
twelfth of its total travel to present a fresh row of empty tubes
11 to the needles 12.
In this way each of the twelve rows of tubes 11 contained in the
dispenser tray 36 is presented to the needles 12 so that if the
first row of tubes 11 contains a quantity of liquid, this liquid
may be introduced into the respective syringes 10 by immersing the
tips of the needles in the liquid and raising the crossbar 16 by
hand, and thereafter dispensed in predetermined quantities into
each of the next 10 rows of tubes 11 as will be described
hereinafter, and the remainder of the liquid discharged into the
last row of tubes 11.
To ensure that the quantity of liquid dispensed on each occasion is
precisely the predetermined amount the head 20 is arranged to move
in a plane which is at a small angle to the vertical so that, as
shown in FIGS. 8 and 8A the needles 12 have an inclined movement
relative to the tubes 11 when the head 20 is moved, and the tips of
the needles 12 are caused to deform when the needles 12 are forced
into the tubes 11, thus preventing dripping from the needles
12.
The first row of tubes 11 may be sealed with special caps having a
pierceable membrane, which when pierced by a needle 12 wipes the
outside of that needle 12 so that on withdrawing the needle 12 from
the tube 11 (which contained liquid to charge the syringe 10) the
outer surface of the needle is free from excess liquid.
The control circuit for this embodiment is shown in FIGS. 7a and
7b, and consists of single phase a.c. supply lines 71 and 72; the
head motor 21 with associated circuits 73 and 74; the
carriage-release or indexing motor 75 drivingly connected with the
indexing bar 43 and with first and second rotary switches 76 and 77
with associated circuitry; a timer motor 80 together with
cam-operated contacts 81 to 88; and a dispenser motor 90 with
associated control circuits. The circuit controls include a
manual/automatic switch (in the manual position of FIGS. 7a and 7b)
having contacts 93, 94, 95 and 96; a start button 99 for the
carriage-release motor 75; an up/down switch, (in the `up` position
in FIG. 7b) having contacts 101 and 102 for the head motor 21; and
a manual start button 103 for the dispenser motor 90.
The circuit 73 controls the direction of rotation of the motor 21
which is a split-phase a.c. motor, the winding connections for
which are shown in FIG. 7A, and includes a reversing relay 105
connected on one side to the supply line 71 by a conductor 106 and
on the other side to the supply line 72 by parallel circuits
consisting of, respectively, the contact 83, a conductor 107 and
the `automatic` position of the contacts 95, and a conductor 109,
the `down` position of the contacts 101, a conductor 108 and the
`manual` position of the contacts 95. The relay 105 has two sets of
contacts 110 and 111. The contacts 110 connect the conductor 112,
which is coupled to the line 72, to one or other terminal of one
winding of the motor 21 and the contacts 111 connect a terminal of
the first winding not connected to the contacts 110. The other
terminal of the other winding of the motor 21 is connected to the
circuit 74 through a conductor 115.
The circuit 74 includes a carriage `start` microswitch 116 to the
common terminal of which is connected the conductor 115. From a
first other terminal of the microswitch 116, a conductor 117 leads
to the common terminal of a head motor central microswitch 118, the
precise height of which, as seen in FIG. 2, can be adjusted by
means of a hand-operable adjusting wheel 119 driving a pinion 120
and a rack 121 to which the microswitch 118 is secured. From a
first other terminal of the microswitch 118 a conductor 123 leads
to a first terminal of the head motor high level microswitch 124
(FIG. 2) the common of which is connected to the supply line 71 by
a conductor 125. Also connected to the first terminal of the
microswitch 124 is a conductor 126 leading to the common of the
contacts 94 of the manual/automatic switch. The `automatic` contact
of the contacts 94 is connected by a conductor 128 to the common of
the contacts 82, the first other contact of which is connected by a
conductor 129 to the second contact of the microswitch 124. The
second other contact of the contacts 82 is connected by a conductor
130 to the second other contact of the microswitch 118. The manual
contact of the contacts 94 connects through a conductor 131 to the
common contact of the contacts 102 of the up/down switch of which
the `down` contact is connected by a conductor 132 and junction 133
to the conductor 129, and the `up` contact connects through a
conductor 134 and junction 135 with the conductor 130.
The second other contact of the microswitch 116 is connected by a
conductor 140 to the common of a normal/special switch 141, the
`special` contact of which connects through a conductor 143 and
junction 144 to the conductor 117. The `normal` contact of the
switch 141 connects through a conductor 145 to the common of a head
motor low level microswitch 146 (FIG. 2), the first other contact
of which connects through a conductor 147 and junction 148 with the
conductor 123 and the second other contact of which connects
through a conductor 149 and junction 150 with the conductor
130.
It can be seen that the motor 21 is energized when the conductor
115 is connected through the circuit 74 with the supply line
71.
Connnected between the conductor 115 and the supply line 72 by
means of a junction 155, a conductor 156, a rectifier circuit 157
and a conductor 158 is the solenoid 159 of the brake 25 (FIG. 3).
The brake 25 is in operation unless the solenoid 159 is energized,
i.e. the brake 25 is on when the motor 21 is de-energized.
The carriage-release motor 75 is connected on one side to the
supply line 72 by a conductor 165, a junction 166 and a conductor
167. The other side of the motor 75 is connected by a conductor
178, a junction 179 and a conductor 180 to one side of the start
button 99. The other side of the start button 99 connects through a
conductor 182, a junction 183 and a conductor 184 to the
`automatic` contact of the contacts 93 of the automatic/manual
switch, the common of the contacts 93 being connected to the line
71. The other side of the start button 99 also connects through a
conductor 186, contacts 81, a conductor 187 and a junction 188 with
the conductor 178. The supply line 71 is connected through a
conductor 190 and a microswitch 191 with the conductor 178, the
microswitch 191 being cam-operated by the carriage-release motor
75. The conductor 184 connects through the contacts 200 of a relay
201 and a conductor 202 with the wiper 203 of the rotary switch 77.
The switch 77 has twelve contacts designated numbers 1 to 10, S
(sample), and W (waste). Contact S and the even-contacts 2 to 10
are connected to a conductor 204 connected with a first contact of
a microswitch 205. The W contact and the odd-numbered contacts are
connected by a conductor 206 with the second contact of the
microswitch 205, the common of which is connected through the motor
80, and the conductor 207 to the supply line 72.
As seen in FIG. 6, the microswitch 205 is mounted on and moves with
the tray-moving arm 40, its contact arm 209 engaging a stepped bar
210 secured to the frame of the dispenser, so that as the tray
moves through the dispenser the microswitch is actuated once for
every tray position.
Reverting to FIGS. 7a and 7b , the manual contact of the contacts
93 is connected by a conductor 211 to the S contact of the rotary
switch 76 which has contacts corresponding to those of the switch
77 and whose wiper 212 is connected by a conductor 213 to the
supply line 71. The coil of the relay 201 is connected between the
conductor 211 and the junction 166.
The numbered contacts of the switch 76 are connected as inputs to a
conventional matrix board 215 which has a number of outputs, in
this embodiment four. Each input can be connected to any output by
means of a plug at the appropriate cross-over points, as is
conventional in such boards. The four outputs from the board 215
together with the conductor 216 are connected to the common
terminal of one of the contacts 84 to 88 which are, as previously
indicated, cam-operated by the motor 80.
The other contacts of each of the contacts 84 to 88 are connected
in common through a conductor 218, a junction 219, a conductor 220,
a junction 221 and a relay 222 to the supply line 72. From the
junction 219, a conductor 225 leads through the button 103 and the
contacts 96 of the automatic/manual switch to the supply line 71.
The `automatic` contact of the contacts 96 connects through a bias
resistor 227 and a pilot light 228 to the supply line 72. From the
junction 221 a conductor 230 leads to the supply line 71 through a
switch 231 which is cam-operated by the motor 90, which also drives
cam 34 (FIG. 4).
The relay 222 controls two sets of change-over contacts 235
operable to connect the motor 90 either to the supply or to the
conductors 236 and 237, connected to the output of a rectifier 238
energized by a supply-connected transformer 239. A bias resistor
240 is included in the conductor 236, a capacitor 241 between the
conductor 236 and the common contact of a microswitch 242 the other
terminals of which are connected respectively to the conductor 237
and, through a relay 243 back to the conductor 236.
The microswitch 242 is operated by the tray-moving arm 40 in its
final position at the end of an operating cycle.
FIG. 7B shows the relationship between the operating cycles of the
contacts 81-88.
The dispensing apparatus is prepared for use by loading a tray of
test tubes into the machine so that the row of sample containing
tubes, located at the front of the tray, are positioned beneath the
syringes 10, this position being readily checked by observing the
reading of a dial 250 (FIG. 6) on the indexing bar 43. The control
circuit is set up as shown in FIGS. 7a and 7b, the `manual`
position of the automatic/manual switch having been chosen.
To load the syringes 10 from the sample-containing tubes 11, the
head 20 is lowered by putting the up/down switch 101 to the `down`
position. This energizes the relay 105, through the circuit supply
line 71, the conductor 106, the relay 105, the conductor 109, the
contacts 101, the manual contact of contacts 95, and the supply
line 72, to change over its contacts 110 and 111. The conductor 115
is energized from the supply line 71, through the conductor 125,
the microswitch 124, the conductor 129, the junction 133, the
conductor 132, the `down` contact of contacts 102, the `manual`
position of contacts 94, the conductor 126, the conductor 123, the
microswitch 118, the conductor 117 and the microswitch 116, to
complete the motor circuit and energize the solenoid 159 to release
the brake 25. The head 20 moves down, immediately actuating the
microswitch 124 to connect directly with the conductor 123, until
it actuates the microswitch 118, thus breaking the connection
through the circuit 74 to the conductor 115, de-energizing the
motor 21 and applying the brake 25 to lock the head 20 in this
position. The crossbar 16 (FIG. 4) is then raised manually to draw
into the syringes 10 liquid from the sample-containing tubes 11. It
should be noted that the head 20 has not been fully lowered so that
the syringe needle tips do not extend to the bottom of the sample
tubes 11, thus obviating the risk of drawing unwanted sediment into
the syringes 10.
The syringes 10 are then primed by depression of the button 103
(FIG. 7b) which completes a circuit from the supply line 71, the
contacts 96, the conductor 225, the junction 219, the conductor
220, the junction 221, the relay 222 to the supply line 72.
Energization of the relay 222 connects the motor 90 to the supply
lines to rotate the cam 34 (FIG. 4) and operate the pawl 18 and
ratchet 17 mechanism of FIG. 4. This, as previously explained,
discharges an accurately measured quantity of liquid from the
syringes 10. The motor 90 remains energized so long as the relay
222 is energized and a hold circuit for this purpose, which
includes the microswitch 231, is closed immediately the motor is
energized and re-opens only after one revolution of the motor's
rotor. De-energization of the relay 222 connects the motor 90
across the d.c. conductors 236 and 237 which in effect brakes the
motor. This priming operation may be repeated two or three times if
desired.
The head 20 is then raised by operating the up/down switch to
change the contacts 101 and 102 to their `up` position. The change
of contacts de-energizes the relay 105 whose contacts 110 and 111
change over to reverse the direction of rotation of the motor 21
and the conductor 115 is energized from the supply line 71 through
the conductor 125, the microswitch 124, the conductor 126, the
`manual` contact of contacts 94, the `up` contact of contacts 102,
the conductor 134, junction 135, junction 150, the conductor 130,
the microswitch 118, the conductor 117, and the microswitch 116.
Initial movement of the head 20 operates the microswitch 118 to
return it to the position shown in FIG. 7b, but the circuit remains
complete through the conductor 125 until the head 20, at the top of
its travel, actuates the microswitch 124 to restore the circuit to
the position shown in FIG. 7b.
The brake 25 is of course operating correctly because of the
energization of its solenoid 159, to release the brake, when
conductor 115 is energized.
The dispensing operation may now commence, the manual/automatic
switch being put to the `automatic` position. Changeover of the
contacts 96 energizes the pilot light 228, and the coil 201 is
energized from the line 71, the conductor 213, the wiper 212, the
conductor 211, the coil 201, the junction 166 and the conductor
167, to open the contacts 200. The start button 99 is now actuated
to complete the circuit from the line 71 through the contacts 93,
the junction 183, the conductor 182, the start button 99, the
conductor 180, the junction 179, the conductor 178, the
carriage-release motor 75, the conductor 165, the junction 166, and
the conductor 167 to the line 72. The motor 75 begins to turn,
immediately operates the contacts 191 through the cam to provide a
hold circuit, drives the wipers from position `S` to position 1, on
the rotary switches and rotates the indexing bar 43. Rotation of
the indexing bar, which is driven by the motor 75 through a 12 to 1
reduction gearing, moves the first pin 42 out of engagement with
the pawl 41 on the tray arm 40 so that, under the bias of its
spring 38, the tray arm 40 and the tray move forward until the pawl
41 engages the second pin 42, i.e. the first empty row of tubes on
the tray 40 is now located beneath the syringes 13. This movement
of the tray arm changes over the contacts of the microswitch 205 as
its contact arm 209 moves down a step on the bar 210.
When the wiper 212 of the rotary switch 76 leaves the S contact,
the relay 201 is de-energized to close the contacts 200. The motor
75 then completes its one revolution and switches itself off by
opening the cam-operated contacts 191. The wipers 212 and 203 of
the rotary switches are now in the 1 position, the latter wiper
completing the circuit through the line 71, the contacts 93, the
conductor 202, the wiper 203, the conductor 206, the microswitch
205, the timer motor 80, the conductor 207 and the line 72.
Energization of the motor 80 commences operation of the cams
controlling the contacts 81 to 88 in sequence.
The first contacts operated are 83 and 82 simultaneously, the
former completing the circuit through the relay 105 to put the
contacts 110 in the down mode and the latter energizing the line
115 from the line 71 through the conductor 125, the contacts 124,
the conductor 129, the contacts 82, the conductor 128, the contacts
94, the conductor 126, the conductor 123, the junction 148, the
conductor 147, the microswitch 146, the conductor 145, the
microswitch 141, the conductor 140 and the microswitch 116 which
has changed its contacts because of the carriage movement. The head
20 thus begins to move down, immediately changing over the contacts
124 to connect the conductors 125 and 123 direct to each other. The
microswitch 118 is not in the circuit so the head continues to its
bottom position where it actuates the low-level microswitch 146 to
break the supply to the motor.
In this position the points of the syringe needles 12 have entered
the first row of empty tubes.
The contacts 84 to 88 are then operated so as to move to their
normally closed position which is in the circuit. It will be noted
that during the previous cycle the contacts had moved
simultaneously to their normally open position which is out of the
circuit. Closure of these contacts completes a circuit from the
line 71 through the conductor 213, the wiper 212, contact 1 of the
switch 76, the board 215, the output of the board 215 associated
with contact 1, the corresponding contact from 84 to 87, the
conductor 218, the junction 219, the conductor 220, the junction
221 and the relay 222 to the line 72. Energization of the relay 222
in this way changes over the contacts 235 and energizes the motor
90 which rotates its cam 34 to discharge a predetermined quantity
of liquid from the syringes 10 and closes, by means of its second
cam, the contacts 231 to provide the hold circuit for the relay
222. After one revolution of the motor 90, the contacts 231 open to
de-energize the relay 222 and shut off the motor if the appropriate
contact 84 to 87 has meantime opened. If the appropriate contact
has not opened the motor 90 commences another revolution, the hold
circuit through 231 again being operative. The motor thus stops
only at the end of a revolution after the appropriate contact 84 to
87 has opened, thus causing the syringes to discharge an integral
multiple of the basic discharge, i.e. 25 microliters, into the
first row of empty test tubes, the multiple being determined by the
closure time of the appropriate contact 84 to 87 and the
appropriate contact being determined by the plug connection in the
board 215.
The contacts 82 and 83 then operate again, the contact 83
de-energizes the relay 105 to return the contacts 110 to the `up`
position and the contacts 82 re-energize the motor 21 to drive the
head to the upper position where it actuates the microswitch 124 to
de-energize the motor 21.
The last contact actuated by the timer motor 80 is the contact 81
which completes an energization circuit for the carriage-release
motor which commences another revolution, switching off the timer
motor 80 by driving the wiper 203 off the 1 contact and switching
the motor 80 on again by driving the wiper 203 onto the 2
contact.
This process continues for the rest of the carriage positions. It
should be noted that contact W on the rotary switch 76 is connected
directly to the contacts 88 which remain closed long enough to
empty the syringes into the last row of waste tubes. On leaving the
waste position the carriage trips the microswitch 242 which
discharges the capacitor 241 through the relay 243, thus tripping
the manual/automatic switch to the manual position and
de-energizing the drive circuits.
The apparatus has thus automatically dispensed specified quantities
of sample into the ten rows of tubes and any remaining sample into
the waste tubes. The apparatus could, of course, be started at any
of the carriage positions if it is desired to use the apparatus
with less than ten rows of tubes.
It may be desirable in certain circumstances that the lower level
of the head 20 be controlled by the control microswitch 118, which
is, of course, adjustable rather than by the lower microswitch 146,
and this facility is provided by the normal/special switch 141
which, in the `special` position effectively short-circuits the
microswitch 146 independently of the position of the microswitch
116.
* * * * *