Abstract: A method for preparing a volume of blood for cellular analysis in a hematology instrument includes the step of gently mixing the blood sample with a reagent and/or diluent using a stream of air. Preferably, the air stream is directed at the liquid(s) to be mixed at a relatively steep angle, preferably less than about 10 degrees from the normal to the liquid surface. A mixing vessel adapted for use in a hematology instrument for carrying out the method of the invention comprises a cap that supports an air jet for directing the air stream at an angle in keeping with the method of the invention.

Abstract: A liquid aspiration device comprises an aspiration tube that slideably engages an opening in a cap such that a head on the end of the aspiration tube is moveable with respect to the opening in the cap. A tube cover is positioned between the opening in the cap and the head of the tube. The tube cover is operable to collapse into the cap when the head is moved into the cap. When the head and the tube cover are moved into the cap they are shielded from potential contamination that may occur when the aspiration device is moved from one container to the next. A lock is positioned in the cap. The lock is operable to move between an engaged position where the head may be retained within the cap and a disengaged position where the head is free to pass into or out of the cap.

Abstract: Apparatus for aspirating liquid from a container, e.g., a test tube, having a puncturable stopper includes a pair of stepper motors that share a common linear actuator or drive member. One motor operates to axially advance the linear drive member (preferably a lead screw) to a position in which it serves to position a rigidly connected tube-detector/stripper member in engagement with the top of a stopper on a tube. Thereafter, the second motor operates to move along the surface of the same drive member to advance an aspiration probe through the engaged stopper and into a liquid aspirating position within the tube. Preferably, a linear guide rail, slidably-mounted on a frame that supports the liquid-aspirating apparatus, serves to guide both the movement of the aspiration probe and the linear drive member. As a result of the shared components, the apparatus is highly precise and reliable.

Abstract: Apparatus and method for aspirating liquid from a container, e.g., a test tube or other vessel, includes apparatus for sensing that an aspiration probe tip is contacting the inside bottom wall of the container, whereby a maximum volume of liquid can be aspirated from the container. According to the invention, an encoder is mounted on the driven member of a motor (e.g., on a rotatably-driven drive shaft or a nut of a stepper or D.C. motor, or on a linearly-driven shaft of a linear actuator) used to rectilinearly advance the probe tip into the container. Such encoder produces a series of pulses indicating the speed and/or linear position of the probe tip. A motor controller responds to a predetermined change in pattern of pulses from the encoder indicating that movement of the probe tip has been resisted by the vessel bottom, whereby further movement of the driven member and of the probe connected thereto is arrested, and the probe tip remains in contact with the vessel bottom.

Abstract: A shear valve assembly comprises a pair of valve pads having opposing planar surfaces supported for relative sliding engagement. Each valve pad defines a plurality of liquid pathways by which a liquid can be passed from one pad to the other. The planar surface of one of the valve pads has an open channel formed therein, such channel having dimensions to accommodate a prescribed volume of liquid. Liquid is introduced into such channel via a first pair of pathways formed in the other valve pad, and liquid is dispensed from the open channel by a second pair of pathways that are brought into alignment with the channel during sliding movement between the valve pads. The valve assembly is particularly useful in blood-analyzing instruments for isolating and dispensing relatively minute volumes (of the order of microliters) of whole blood for analysis.

Abstract: A method for preparing a volume of blood for cellular analysis in a hematology instrument includes the step of gently mixing the blood sample with a reagent and/or diluent using a stream of air. Preferably, the air stream is directed at the liquid(s) to be mixed at a relatively steep angle, preferably less than about 10 degrees from the normal to the liquid surface. A mixing vessel adapted for use in a hematology instrument for carrying out the method of the invention comprises a cap that supports an air jet for directing the air stream at an angle in keeping with the method of the invention.