A fluid mixing apparatus (10) for combining into a uniform mixture at least two liquid components includes a reciprocating left positive displacement pump (18) and a reciprocating right positive displacement pump (20) isolated from the left pump (18). The left pump includes a first metering cylinder (22) associated with a first liquid component and a second metering cylinder (24) associated with a second liquid component. The right pump (20) includes a first metering cylinder (26) associated with the first liquid component and a second metering cylinder (28) associated with the second liquid component. While the left pump (18) is measuring a predetermined volume of the first and second liquid components, the right pump (20) is pumping a predetermined volume of the first and second liquid components to a receptacle (14), and vice versa for when the right pump (20) is measuring in order to provide a continuous flow of the first and second liquid components to the receptacle (14).

An automatic dilutor consisting of an upstanding calibrated diluent barrel with a lower intake portion adapted to be supported in a diluent container and having an intake check valve. A main diluent plunger is provided in the barrel and develops suction when moved upwardly. The plunger has an enlarged top operating portion with a depending diluent-metering rod on which a diluent indicating lens is adjustably mounted, being engageable with a top flange on the barrel to limit extension of the plunger in accordance with the desired amount of diluent to be dispensed. A branch conduit connects the diluent barrel through another check valve with an upstanding calibrated reagent-aspirating barrel having an outlet conduit connected to its bottom portion. An aspirator plunger is provided in the aspirating barrel, the aspirator plunger having an enlarged top end with a depending reagent-metering rod on which another indicating lens is adjustably mounted, being engageable with a top flange on the aspirating barrel to limit extension of the aspirator plunger in accordance with the amount of reagent to be dispensed. The diluent indicating lens is yieldably connected to the reagent-metering rod so that the aspirator plunger will move upwardly only to its limit when the diluent plunger is moved upwardly to its limit, simultaneously drawing the preset desired amounts of diluent and reagent respectively into the diluent barrel and the aspirating barrel. When the diluent plunger is then moved downwardly to its bottom position, the connection between the diluent indicating lens and the reagent-metering rod causes the preset amounts of diluent and reagent to be simultaneously discharged through the outlet conduit.

A device is provided comprising in combination a support frame, a block or interchangeable element mounted on the frame, a pair of pistons carried by the block and reciprocated by a motor mounted on the frame, a set of ducts and valves connecting the pistons with a drawing reservoir, a delivery duct, and threaded stems to change the stroke of each of the pistons and consequently the amount of the drawn and delivered liquid.

The invention relates to an automatic precision pipetting device. The inventive device comprises at least two cylinder/piston-type pumping units (1, 2), the rods of which are rotated by means of a common motor unit (MP). Moreover, the pumping chamber of each of the pumping units (1, 2) is connected to a circuit comprising, successively, a conduit that opens into a container of rinsing liquid (RL), three successive solenoid valves (EV.sub.1, EV.sub.2, EV.sub.3) and a portion of circuit which connects the second solenoid valve (EV.sub.2) with the pipetting means (AP). The larger pumping chamber is connected in the part of the circuit that provides the connection between the two solenoid valves (EV.sub.1, EV.sub.2) while the second pumping chamber is connected to the above-mentioned portion of circuit by means of a connector, said portion of circuit comprising a solenoid valve (EV.sub.3) which is disposed between said connector and the aforementioned pipetting means. The invention is suitable for reagent reconstitution, in particular, in an automatic analysis device.