Liquid quantitative dispensing apparatus for withdrawing liquid like a syringe into a plurality of pipettes arranged in rows, by simultaneously pressing and releasing cap-like projections formed of flexible material and dispensing the liquid to test tubes and the like.

A Multiple Sample Pipetting Device is disclosed which is adapted to remove small predetermined volumes of liquid from a plurality of sample wells arranged in a compact rectilinear array, or conversely to transfer small predetermined volumes of liquid from one large reservoir container to a plurality of sample wells arranged in the same array. The apparatus has a plurality of small tubes extending downwardly with the upper end portion communicating with reservoirs that have a predetermined volume. A flexible diaphragm extends across all of the reservoirs, and the upper ends thereof are in communication with a common manifold chamber. The application of positive or negative pressure moves the diaphragm downwardly and upwardly into contact with the lower and upper reservoir walls, respectively, and either extracts or expels liquid from the tubes. The manifold and tube holding portion of the apparatus is vertically movable so that the tubes can be lowered into the appropriate container to extract the predetermined volume of liquid material.

A pipetting device comprising a housing and a plurality of tubes mounted on the housing. The housing has a manifold chamber and a plurality of passages leading from the tubes, respectively, to the manifold chamber. A flexible impervious membrane extends across the passages to divide each of the passages into a first passage section and a second passage section. The first passage sections provide communication between the tubes and one side of the membrane, and the second passage sections provide communication from the other side of the membrane to the manifold chamber. A substantially incompressible flowable material, such as a liquid, fills the second passage sections and the manifold chamber. A mechanism is provided for moving the flowable material to deflect the membrane in opposite directions whereby liquid can be drawn into, and expelled from, the tubes.

A multi-pipette system of the type having sample volume determined by size of cavities into which flexible membrane portions are drawn, provides a microporous block with the cavities formed in it for drawing the flexible membrane into the cavities when pressure is reduced above the microporous block. Slide-in-place location and replacement is provided for supply containers, disposable tube arrays for drawing up samples and for expelling them, and for flexible membranes. In an embodiment microporous block cavity size is adjustable.

In known methods for generating a predetermined constant pressure in a test liquid of a test apparatus, the test liquid is acted upon by compressed gas that is pumped continuously by a pump and is vented into the atmosphere once the test procedure is completed. This not only makes for an expensive consumption of compressed gas but also causes fluctuations in the pressurized liquid and generates noise. In this method, the pressurized liquid is pumped into a reservoir by a feed pump and in the process, via a movable wall, positively displaces compressed gas, which can flow back into a compressed gas container via an opened bypass shutoff valve, a bypass line, and a compressed gas shutoff valve. During the procedure of testing the specimen, the compressed gas from the compressed gas reservoir acts upon the test liquid with a constant pressure, regulated via the pressure regulating valve. The method is especially suitable for use in a test apparatus for testing injection valves and Diesel injection nozzles.