Laboratory Microtitration Dispensing Apparatus

Abstract

Laboratory dispensing apparatus including a base, a liquid reservoir and well assembly mounted rearward the base, and a microtitration plate carrier device mounted on the base for horizontal movement between a forward retracted position and a rearward operative position overlying a portion of the well. A novel vertically movable dispensing assembly is positioned above the base in operative alignment with the portion of the liquid well so that with the carrier in the forward retracted position the dispensed assembly may withdraw microquantities of liquid from the well and then dispense the same into the microtitration plate wells when the carrier is moved to the rearward position. The dispensing unit includes a novel pump piston actuator assembly and pneumatic control system which enable microquantities of liquid to be simultaneously and accurately picked up and dispensed from the dispensing needles or pipettes.

Description

BACKGROUND OF THE INVENTION

This invention is related generally to laboratory analyzing and titrating apparatus and more particularly to a sampling and dispensing apparatus capable of precisely and simultaneously withdrawing into a plurality of needles or pipettes predetermined reproducible microquantities of liquid such as a diluent, from a liquid source and delivering the same to a plurality of corresponding wells of a microtitration plate.

In the laboratory, quite often it is necessary to perform analytical and/or experimental tests or procedures on large number of laboratory specimens, the procedures frequently involving the measuring and dispensing of microquantities of liquid in the nature of 0.025 milliliters. It is, of course, desirable that such procedures be performed within a minimum amount of time and with exactitude and precision to eliminate error.

In the past, laboratory tests of this nature have generally been performed manually and individually and have required a great deal of time and effected inaccurate and undependable results. An operator simply could not time after time reproduce with accuracy the microquantitative liquid measurements necessary for these tests, nor could he perform an adequate number of tests within a reasonable period of time.

Automatic laboratory devices have been developed in an attempt to overcome these problems, but such devices have generally been very complex structurally and prohibitively costly. Additionally, they have not operated entirely satisfactorily to minimize time while providing extreme accuracy. Typical prior-art systems are those described in U.S. Pat. Nos. 3,188,181 3,261,208; 3,264,800; and 3,327,535.

SUMMARY OF THE INVENTION

It is a primary object of this invention to provide a novel compact laboratory dispensing machine which simultaneously withdraws from a liquid reservoir into each of a plurality of needles or pipettes a predetermined reproducible microquantity of liquid, e.g., a drop of 0.025 milliliter, and simultaneously dispenses the same into corresponding specimen containers or wells of a microtitration plate.

Another object resides in the provision of a compact laboratory dispensing machine in which a liquid supply source is readily mounted as part of the machine and the microtitration plate is movably mounted to permit the pipettes to first withdraw precise microquantities of liquid from the supply source and then dispense the same into the corresponding microtitration plate wells.

Still another object is to provide a laboratory dispensing machine capable of serially diluting precise microquantities of antigens by serially transferring and mixing the antigen with diluent in successive rows of wells of a microtitration plate.

A further object is to provide a novel pickup and dispenser unit including a plurality of pipettes or needles having associated actuator assemblies of novel construction to permit the simultaneous pickup and discharge of precise reproducible microquantities of liquid from the needles. A still further object is to provide a novel simplified pneumatic control system for activating the actuator assemblies to control the pickup and dispensing of fluid from the plurality of pipettes and for accurately and precisely determining the exact microquantities of fluid to be dispensed.

Still another object resides in the provision of simple compact laboratory machine which includes a novel hand manipulatable vertically movable pickup and dispensing unit having a plurality of pipettes, a liquid reservoir and well assembly mounted on the base underneath the pipettes, and a movable microtitration plate carrier member slidable between forward and rearward positions and in the rearward position being located vertically above the well with the microtitration plate wells aligned with corresponding pipettes. This arrangement permits the dispensing unit to first pick up liquid from the well when the carrier is in the forward position and then to dispense the liquid into the titration plate wells when the carrier is moved to its rearward position underneath the pipettes.

Further objects and advantages will become apparent from the following detailed description of a preferred embodiment and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the laboratory dispensing apparatus of the invention with the various parts shown in the retracted inoperative position;

FIG. 2 is a front elevational view of the apparatus of FIG. 1;

FIG. 3 is a side elevational view of the apparatus of FIG. 1;

FIG. 4 is a top plan view of the apparatus of FIG. 1;

FIG. 5 is a fragmentary elevation section taken along line 5-5 of FIG. 4 and illustrating the pickup and dispenser assembly in its lower position in which it picks up liquid from the liquid well;

FIG. 6 is a fragmentary elevation section taken along line 6-6 of FIG. 4 illustrating the microtitration plate in its operative position in which the pickup and dispenser assembly is lowered with the dispensing needles positioned within the wells of the titration plate;

FIG. 7 is an enlarged fragmentary sectional view illustrating a pump piston actuator assembly within the pickup and dispenser head plate with the piston actuator assembly in its normal retracted position;

FIG. 8 is a view similar to FIG. 7 but showing the piston actuator assembly in its operative dispensing position;

FIG. 9 is an exploded sectional view of the piston actuator assembly illustrated in FIGS. 7 and 8;

FIG. 10 is an exploded perspective view of the reciprocating plate carrier and the microtitration plate locator positioned on the carrier;

FIG. 11 is a perspective view of the reservoir and well base;

FIG. 12 is a perspective view of a modified well for the reservoir and well base;

FIG. 13 is a sectional view taken along line 13--13 of FIG. 12;

FIG. 14 is a front elevational view partially broken away illustrating the air control assembly used with the pickup and dispensing apparatus of the invention;

FIG. 15 is a top plan view of FIG. 14 but partially broken away;

FIG. 16 is a sectional view of a flow restrainer orifice used in the control assembly of FIGS. 14 and 15;

FIG. 17 is a schematic diagram of the overall air control system incorporated within the pickup and dispensing unit of the invention;

FIG. 18 is a perspective view of a modified pickup and dispenser assembly including only a single row of dispensing needles particularly useful in serial dilution processes; and

FIG. 19 is a perspective view of a single pickup and dispensing needle or syringe incorporating the novel piston actuator assembly shown in FIGS. 7--9.

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings, the laboratory pickup and dispensing apparatus of the invention comprises a rectangular base 20 having corner mounting pads 21, a pickup and dispenser assembly 22 mounted above base 20 by vertical post 24, control gear housing 26, gear rack 28 mounted within housing 26 and driven by pinion 30, and L-bracket 32 secured to the threaded bottom end of rack 28 by nut 34 and to the rear of dispensing assembly 22 by screws 36. The pickup and dispensing assembly is moved vertically relative to base 20 by rotating handle 38 which rotates pinion 30 to drive rack 28.

A sample carrier plate 40 having side flanges 42 (FIG. 4) is slidably mounted within longitudinal recesses 44 in guide rails 46 and 47 which are spaced above base plate 20 by spacers 48. As shown in FIG. 2, spacers 48 are internally threaded to receive a top screw 50 which secures the rails to the spacers and bottom screw 52 which holds the spacers to base 20. Carrier 40 has a knob 54 by which an operator may slide the plate from its forward retracted position shown in FIGS. 1 and 5 to its rearward operational position underneath the dispensing assembly as shown in FIG. 6.

The carrier plate 40 may support a plurality of separate vials or tubes or may suitably support a transparent microtitration plate 140 having a plurality of wells 142 and being generally constructed similar to the microtitration plates disclosed in U.S. Pat. No. 3,356,462. When the latter is used, carrier 40 is provided with a titration plate locator and guide assembly shown in FIG. 10 including a rectangular plate 144 fixed to carrier 40 by rivets 146, the upper projecting ends of which serve as locator pins received within the cutout corners 148 of hollowed locator 150 on which the titration plate 140 rests as shown in FIGS. 5 and 6. The sides of the titration plate overlap the sides of locator 150 with the base of the wells 142 resting on the bottom of locator 150. This locator assembly enables an operator to readily replace one titration plate for another and ensures that the wells 142 of the titration plate will be accurately aligned with their respective corresponding needles 128 during a dispensing operation.

Also mounted on base 20 is a liquid or reagent reservoir well plate 56 (FIG. 11) positioned on the base by an end recess 58 which engages guide pin 60 secured to the base and by a locking pin 62 which passes through guide rail 47 into a hole 64 in well plate 56. Well plate 56 mounts a liquid reservoir tank 66 connected by cylindrical recess 72 and channel 68 to a supply well 70 located underneath dispenser assembly 22. Tank 66 is an inverted cylindrical container disposed within cylindrical recess 72 in well plate 56 with its mouth aperture 74 defined by protuberant plug 76 opening into counterbore 78 communicating through channel 68 with trough 70. The reservoir maintains the liquid in trough 70 at a constant level and also prevents undesirable liquid overflow in well-known manner through the vacuum formed when plug 76 becomes fully immersed to prevent air from bubbling upwardly through mouth aperture 74.

With particular reference to FIGS. 5 and 6, the pickup and dispenser assembly 22 includes an air manifold comprising a rectangular body member 80 having a central main longitudinally directed passageway 82 intersected by a plurality of transverse or cross passageways 84 plugged at opposite ends 86. Passageways 84 also are intersected by vertical downward passageways 88. A conduit fitting 90 threadedly engages one end of passageway 82 and receives an air conduit 92 to deliver air into manifold 80 from a suitable regulated air source and exhaust air therefrom in a manner to be described.

Connected to the bottom of manifold 80 by screws 94 is a rectangular dispenser head plate or member 96 having a top rectangular recess 98 receiving a thin flexible diaphragm 100 which separates a plurality of stepped circular apertures 102 from aligned manifold passageways 88.

As shown in detail in FIGS. 7--9, stepped aperture 102 comprises increasingly diametered circular sections 104, 106, 108, respectively and houses a needle piston actuator assembly 109 including a piston sleeve 110 having an end tapered tubular stem 112 which passes through aperture section 104 and a circular hollow head or skirt portion 114 received within section 108 and biased upwardly into sealing engagement with diaphragm 100 by spring 116 positioned within section 106.

A pump piston 118 is in the form of a rod 120 received in tubular stem 112 and a head 122 positioned in skirt 114. A spring 124 located in the upper increased diameter stem section 113 rests on shoulder 113a and biases piston 118 upwardly to engage head 122 with diaphragm 100.

As shown in FIGS. 7 and 8, a chuck 126 snugly engages the end-tapered stem 112 and communicates the hollow stem with the tubular dispenser needle 128 received and supported within its lower end.

The number of dispenser needles 128 provided in the dispenser assembly 22 of the invention may be varied as desired or required, and in the embodiment illustrated there are 96 dispenser needle assemblies aligned in 8 rows of 12 needles each. The number of wells 142 in the microtitration plate 140 of course correspond to the number of dispenser needles provided in assembly 22.

Piston sleeve 110 has its tubular stem 112 and cavitied head portion 114 accurately machined to close tolerances to cooperate with similarly machined pump piston 118 to provide for the displacement of a predetermined exact microquantity of air from the needle assembly 109 as piston 118 moves from the normal position shown in FIG. 7 to the dispensing position of FIG. 8. In this manner, the amount of liquid withdrawn from well 70 by each of the needles 128 and subsequently dispensed therefrom is accurate and reproducible through a series of dispensing operations.

Stop rods 130 are threadedly secured to the bottom of diaphragm plate 96 and, as shown in FIG. 5, cooperate with the circulate top recesses 65 in well plate 56 to determine the depth of immersion of needles 128 in the liquid in well 70 and prevent the needle from contacting the bottom of the well when liquid is withdrawn into the needles. Similarly, as shown in FIG. 6, when the liquid is dispensed from the needles into the microtitration plate wells 142, rods 130 abut the top of the sides of plate 140 to prevent the needles from contacting the bottom of wells 142.

The air supplied to dispensing manifold 80 through conduit 92 is controlled by the control assembly 150 illustrated in FIGS. 14--16, with the overall control function accomplished as shown in the schematic diagram of FIG. 17. The control assembly 150 includes a housing 152 and base 154 on which are mounted a pressure regulator 156 which received compressed air from a suitable source 157 through conduit 158 and passes it at a reduced regulated pressure preferably about 20 psi, to an electrical solenoid operated air valve 160. Valve 160 has an exhaust outlet 161 to atmosphere which is normally closed when the valve is open, but which opens when the valve 160 closes to exhaust the air in manifold 80 and conduit 92 to atmosphere.

The solenoid valve is energized from a terminal board 162 connected to a suitable socket 164 which receives the plug of an electrical cord 166 through which the flow of electrical current from a 115-volt AC power source is controlled by a footpedal-operated switch 170.

A dial pressure gauge 172 connected to reducing valve 156 by suitable L-shaped piping 174 provides an indication of the pressure of the air being supplied to solenoid valve 160 and dispenser manifold 80.

A conduit fitting 176 houses a fixed orifice flow restrainer 178 (FIG. 16) having an orifice 179 which accurately controls the air flow rate from valve 160 to conduit 92 and manifold passageway 82 so that a predetermined fixed reproducible volume of air is supplied to the manifold to ensure that accurate and reproducible microquantities of air may be displaced from each needle assembly 109 and similar quantities of liquid may be picked up by the needles from well 70 and dispensed therefrom into the microtitration plate wells 142.

A typical dispensing operation is as follows. Initially, the respective parts are shown in FIGS. 1--3 with the carrier 40 and titration plate 140 in the forward retracted position and the pickup and dispenser assembly 22 in its raised position.

Footpedal switch 170 is then closed to pass electric current to solenoid terminals 162 to open air valve 160 and pass compressed air at a controlled rate of flow to manifold passageway 82. The air then passes through passageways 84 and 88 to the top face of diaphragm 100 which deforms downwardly into piston sleeve skirt 114 and causes each of the 96 pump piston assemblies to move from its normal position of FIG. 7 to its depressed position of FIG. 8, this movement causing a predetermined accurate quantity of air inside piston sleeve 110, chuck 126, and needle 128 to be displaced therefrom to atmosphere.

The handle 38 is then rotated to lower assembly 22 and immerse the tips of needles 128 in the liquid in well 70 as shown in FIG. 5 with the stops 130 determining the depth of immersion of the needles in the liquid. The foot pedal is then released, closing air valve 160, and exhausting the compressed air from manifold 80 back through conduit 92 and flow restrainer 178 to atmosphere through valve vent 161. When this occurs, diaphragm 100 and piston 118 of each of the needle assemblies are biased upwardly back to the position of FIG. 7 causing a predetermined, accurate microquantity of liquid e.g., 0.025 milliliter, to be drawn into each needle 128 from well 70.

Handle 38 is then rotated in the opposite direction to raise the pickup and dispenser assembly 22 back to the phantom position of FIGS. 5 and 6. The operator next slides the carrier plate 40 to its rearward operative position underneath and aligned with assembly 22, which is then lowered to the dispensing position of FIG. 6. The foot switch 170 is again actuated to depress the pump piston as in FIG. 8, thus forcing the liquid from needles 128 into the corresponding wells 142. The needles are then raised out of the wells and the foot switch released to exhaust the air from manifold 80 to atmosphere as described above.

It has been found that when a liquid having a relatively low viscosity is being handled, small quantities of the liquid from well 70 may adhere to the outside surface of the needles 128, thus resulting in somewhat inaccurate and uncontrollable amounts of liquid being withdrawn from the well. To overcome this, the modified well 70a shown in FIGS. 12 and 13 may be used.

Well 70a is provided with a plurality of partitions 180 having circular side recesses 182 with the opposing recesses of adjacent partitions forming needle pockets 184 which are sized to be sufficiently larger than the diameter of the needles so that the created surface tension in the pockets pulls the diluent liquid off the outside of the corresponding needles. For example, in one operation, with the outside diameter of needles 128 being 0.065 inches, a pocket diameter of one-quarter inch was found to effectively result in removal of excessive diluent from the needle exterior surface. In addition, the height of the partitions is such that the liquid level in the well 70a will not extend over the top ridges of pockets 184 and with a liquid depth of five thirty-second inches, a height of three-eighths inch has been satisfactory.

The invention may also be used to serially dilute microquantities of liquids, such as antigens by using a pickup and dispenser assembly 222 illustrated in FIG. 18, which is constructed exactly the same as assembly 22, except that it includes only a single row of needles 228. Pickup and dispenser head 222 is suitably connected to the bottom end of rack 28 to that the needles 228 are located at an intermediate position above base 20 sufficiently forward of rod 24 to permit each of the rows of titration wells 142 to be successively aligned with the needles as the carrier plate 40 and titration plate 140 are moved from their forward to their rearward position. Conduit 292 may be suitably connected to a valved nipple 294 of T-fitting 93 (see FIG. 17) to provide compressed air for the pickup and dispensing operation.

In a serial dilution process, initially with the carrier plate 40 in the forward inoperative position, the needles 228 are provided with precise microquantities of antigens to be diluted either from well 70 or from a separate row of vials or test tubes (not shown). Similarly, each of the wells 142 is provided with predetermined amounts of diluent.

Next, plate 40 is moved rearwardly so that the first row of wells 142 aligns with needles 228 which are then lowered to dispense the antigen into the wells where they become thoroughly mixed with the diluent by a jet action accomplished by alternately dispensing and picking up the diluted combined mixture from the wells. Precise microquantities of this mixture are withdrawn into the needles 228 which are then raised to permit the next row of wells to be aligned therewith and the diluting and mixing action to again take place. This procedure is repeated for each successive row of wells so that the final mixture in each successive row of the series is more dilute than that in the previous row.

When the last row of wells has been diluted, any quantity of liquid mixture remaining in the needles 228 is discarded and the needles subsequently cleaned by alternately picking up and dispensing distilled water or any other acceptable purging solution from a suitable source.

It is a that a single, hand portable pickup and dispenser needle or syringe 250 illustrated in FIG. 19 having the same manifold and needle assembly structure as that shown in FIGS. 7 and 8 may be provided for such operations as dilution or dispensing of a single specimen or transfer of a single sample to a microscope slide for viewing a precisely metered micro sample of liquid in preparation for seriological testing or microscopic observation.

The syringe 250 may be connected to a valved nipple 252 of T-fitting 93 by conduit 254 to supply air for operation of the syringe.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

I claim:

1. Dispensing apparatus comprising a base, liquid reservoir means comprising a portion of said base, carrier means mounted on said base for horizontal movement between a first nondispensing position at one side of said liquid reservoir means and a second dispensing position in which said carrier means overlies a portion of said liquid reservoir means, liquid receptacle means supported on said carrier means, pickup and dispensing means mounted on said base in operative alignment above said portion of said reservoir means, means for moving said pickup and dispensing means vertically relative to said base, whereby, when said carrier means is in said first position, said pickup and dispensing means may be lowered to a first position to withdraw liquid from said portion of said reservoir means, then raised to permit said carrier means to be placed in said second position, and then lowered to a second position to dispense the withdrawn liquid into said receptacle means.

2. Dispensing apparatus as in claim 1, said pickup and dispensing means comprising a plurality of dispensing needles and means operative to simultaneously withdraw microquantities of liquid from said reservoir into said needles and then simultaneously dispense the same into said receptacle means.

3. Dispensing apparatus as in claim 2, said liquid receptacle means comprising a microtitration plate having a plurality of wells corresponding in number to the number of said dispensing needles, means on said carrier means for positioning said microtitration plate to ensure that said needles and wells are operatively aligned when said carrier means is moved to said second position.

4. Dispensing apparatus as in claim 2, said pickup and dispensing means comprising manifold means having a centered main air passageway intersected by a plurality of side-by-side related angularly directed passageways each of which is intersected by a plurality of generally right angularly related passageways, head means connected to said manifold and having a plurality of apertures aligned with said vertical passageways but separated therefrom by flexible diaphragm means, an actuator assembly mounted in each of said apertures and including piston means normally biased to maintain said flexible diaphragm means out of its respective one of said apertures, means connecting a dispensing needle to each of said actuator assemblies, and means for supplying air to and exhausting air from said manifold passageways whereby the differential pressure on opposite sides of said diaphragm means expands said diaphragm means into each of said plurality of apertures and activates each said actuator assembly to simultaneously pick up from said reservoir means into and thereafter simultaneously dispense from said needles predetermined volumes of liquid.

5. Dispensing apparatus as in claim 4, said head means apertures each comprising a plurality of cylindrical sections of respectively greater diameter from the bottom to the top of said dispensing head means, each said actuator assembly includes a chuck having a tubular stem extending downwardly through the bottom section of said aperture, an enlarged hollow head portion located within the top section thereof, spring means positioned within an intermediate section for biasing said head portion upwardly into sealing engagement with said diaphragm means, said piston means being slidably mounted within said chuck and comprising a rod within said tubular stem and a piston head of lesser axial length within said enlarged hollow head portion, and spring means mounted between said chuck head end wall and said piston head biasing said piston head into engagement with said diaphragm means, whereby when said diaphragm means is displaced in response to the air pressure in said manifold said piston means is moved to dispense fluid from said needle.

6. Dispensing apparatus as in claim 4, said air supply means comprising an air pressure source, pressure regulating means connected to said source and regulating the pressure of air supplied to solenoid operated air valve means, conduit means connecting said air valve means to said manifold main passageway, flow restrainer means located in said conduit means and controlling the flow rate of air therethrough, and switch means operative to pass electrical current to said solenoid operated air valve means to open said valve means and pass air through said flow restrainer means to said manifold main passageway.

7. Dispensing apparatus as in claim 6, said valve means comprising vent means operative when said valve is closed to exhaust said manifold passageways and said conduit means to atmosphere.

8. Dispensing apparatus as in claim 2, said pickup and dispensing means comprising manifold means, a pipette head unit for supporting said dispensing needles, flexible diaphragm means operatively positioned between said manifold means and pipette head unit, said manifold means having air passage means leading to one side of said diaphragm means, and a pneumatic supply system connected to said air passage means for actuating said diaphragm means to simultaneously pick up predetermined quantities of liquid from said reservoir means into said needles and thereafter simultaneously dispense the quantities of liquid from said needles.

9. Dispensing apparatus as in claim 1, said liquid reservoir means comprising a trough positioned underneath said pickup and dispensing means, a liquid supply tank remote from and communicating with said trough through a well and connecting channel, outlet means on said tank controlling the flow of liquid therefrom to said well to maintain the liquid level in said trough at a substantially constant level.

10. Dispensing apparatus as in claim 9, said trough including a plurality of partitions having aligned circular side recesses, the opposing recesses of adjacent partitions defining a plurality of needle pockets which function to eliminate adherent liquid from the external surfaces of said dispensing needles when said needles are raised out of said trough.

11. Dispensing apparatus as in claim 1, wherein said base comprises a rectangular platelike member having an upstanding support post disposed at the opposite side of said liquid reservoir means and said means for moving said pickup and dispensing means comprises a control gear housing carried by said post in vertically upwardly spaced relation to said platelike member and mounting a vertically movable rack gear carrying at its lower end a bracket fixedly mounting said pickup and dispensing means and pinion gear and shaft means including a handle member for selectively rotating said pinion gear and shaft means in a direction to first drive said rack gear to position said pickup and dispensing means in said first position, then in an opposite direction to its raised position, and finally in said first direction to said second position, said first and second positions being predetermined by dependent stop rods carried by said pickup and dispensing means for end abutting engagement respectively with said portion of said base in said first position and with the top wall of said liquid receptacle means in said second position.