US 3683977 A
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.
Description (OCR text may contain errors)
United States Patent 1 51 3,683,977 Crowe et al. [451 Aug. 15, 1972 1541 LIQUID DISPENSING APPARATUS 2,562,815 A 7/1951 Oscroft... ..141/178 x.
2,741,974 4/1956 Avery ..141/181 x  gaff 2,765,817 10/1956 Grzenkowski Switzerland etal i X a 7, 7 2,882,014 4/1959 Addison ..74/1.5 x  Ass1gnee: Beckman Instruments, Limited, 2,932,330 4/1960 Donofrio ..141/178 Glenrothes, Great Britain 1 1 1 y 15 EXGHliMF-EdWQI'd Earls 1' Appl. No.: 37,500
Boruch ..141/130X Y Attorney-Robert J. Steinmeyer and Thomas L. Peterson 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 dispensingfluids therefrom. A precision ground rack and paw] 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.
5 Claims, 12 Drawing Figures PATENTEDAUB 15 I972 SHEET 1 OF 9 HHWMWH Inventor A flurm'y PATENTEDAUB 15 m2 3' 683' 977 sum 2 or 9 Inventor :1 Hurm'y PATENIEDAummn 3.683377 SHEET30F9 P I Inventor Attorney Inventor Attorney PATENTEDAus 15 m2 SHEET 6 [IF 9 Inventor Alforney PATENTEDAus 15 m2 SHEET 9 OF 9 r. O I. n e U n l A Home LIQUID DISPENSING APPARATUS 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.
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; I
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 is mounted on two laterally-spaced slideway guides 23 which are inclinedat 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 16and 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 (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 1 1.
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 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 spacedapart and circumferentially spaced from one another by so that when the bar 43 is rotated through 30 (i.e. one twelfth of a revolution) the arm is movedor indexed forwards by one twelfth of its total travel to present a fresh row of empty tubes 1 1 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 thetips 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 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 1 1 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 liquidto 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, and 96; a start button 99 for the carriagerelease 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, aconductor 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 1 15.
The circuit 74 includes a carriage start microswitch l 16 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 1 18, 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 1 18 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 40 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 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 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, andthe 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 21 1 andthe 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 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 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 and 111. The conductor 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, tie-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 2420, 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 themotor is energized and re-opens only after one revolution of the motors rotor. De-energization of the relay 222 connects the motor 90 across the dc. 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 .1 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 camoperated 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 overthe 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 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 to'return the contacts to the up position and the contacts 82 reenergize the motor 21 to drive the head to the upper position where it actuates the microswitch 124 to deenergize 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 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 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 thelowering said head in a substantially vertical direction relative to said support;
at least one syringeinounted 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 andinitiating 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.