Abstract: A zero backlash device. The device includes a spring loaded bracket for providing a lateral force to the driving nut on a threaded rod. This lateral force is directed perpendicularly to the axis of the threaded shaft thus insuring continued intimate contact between the threads on the driving nut and the threads on the shaft.

Abstract: A shear valve obtaining selective fluidic communication between fluid ports formed in a first member and fluid ports formed in a second member comprises a first seal with means for providing a fluidic seal between aligned ports and which separates the first and second members to form a passage, and a second sealing means to obtain a fluidic seal between the first and second members and enclose the passage. A fluid port is provided to introduce wash solution into the passage formed between the first and second members and a drain port is provided to remove the wash solution introduced between the first and second members, so that a wash and purge operation may be performed to cleanse the sealing surfaces of the valve.

Abstract: Plunger operated pipet operable to execute successive fluid pickup and fluid discharge operations or strokes. A signalling system is provided which signals the occurrence of the second or fluid dispensing stroke of the plunger movement.

Abstract: A method for driving a stepper motor. The method includes varying the width of the high level drive impulses of a bi-level drive system based on the desired speed to be achieved by the stepper motor. A microprocessor is used to vary the pulse width.

Abstract: A passive solar system for temperature control of the air inside homes and other buildings, comprising a pool of water to receive, store and dispense energy from direct sunlight passing through a glass wall, to strike the surface of the water in the pool. The pool has open connecting passage under its bottom and vertically along one of its sides, to form a convective conduit in which cold air is heated by the stored heat of the pool. Adjustable passages are placed through interior walls for convective flow of the pool-heated air into all desired parts of the building. The glass wall is advantageously placed for maximum incidence of heating sunlight upon the pool in winter, and maximum shading of the pool in the summer. A retractable eave may be provided to enhance these effects. During summer days, the pool serves as a heat sink, cooling the interior air.

Abstract: Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body.

Abstract: Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body.

Abstract: A stepper motor positioning control utilizing phase detection of the stepper motor windings. The device utilizes crude positioning apparatus to position the attached turntable or the like in an approximate position. The phase detection of the stepper motor windings is then used to position the attached turntable in the exact location desired.

Abstract: A magnetic stirring arrangement for stirring sample material held within a cylindrical glass sample container for assay. A stirring element within the container is retained in a fixed orientation by an external magnetic field. The container and the contents thereof are rotated in place causing the container contents to be stirred by rotational motion around and past the fixed stirring element.

Abstract: A containment apparatus for liquids. The device may be used with nephelometric instruments to contain sample liquids for serial dilution. The containment apparatus includes a tray section having a plurality of wells formed as an integral part of the tray section. The wells include well portions extending from the tray section such that the well portions are insertible into holes in the turntable rim to secure the tray section to the rim.

Abstract: Apparatus for conveying a blood sample through a flow cell which measures characteristics such as pH, PCO.sub.2, and PO.sub.2 of the sample and for pumping a wash solution through the cell between samples. The flow cell inlet is selectively connected (1) to a sample-filled syringe for driving sample through the flow cell or (2) to a reservoir of the wash solution. The flow cell outlet is connected by a conduit to a waste receptacle. A rotor of a combined peristaltic pump and valve coacts with an elastomeric tubular section of the conduit. The rotor and the elastomeric section are movable in a transverse direction relative to each other between (1) a first or pumping position wherein the rotor compressively engages the section for pumping fluid wash solution through the cell and the conduit and (2) a second or relaxed position wherein the rotor is released from the section to provide an open unrestricted channel for the flow of sample driven by the syringe through the cell.

Abstract: Apparatus for automatically and selectively supplying a blood sample or a wash/calibration solution to the entrance port of a flow cell which measures characteristics of the sample such as pH, pCO.sub.2 and pO.sub.2. A sample filled syringe and a solution supply conduit are supported by respective first and second fluid delivery mechanisms which rotate to move the syringe outlet and the conduit outlet in generally arcuate paths toward and away from the flow cell entrance port. The delivery mechanisms are rotated simultaneously, one toward and one away from the entrance port, by a common drive gear. Seating of the wash solution outlet in the entrance port is upstream of the seating of the sample outlet to ensure complete flushing of sample from the entrance port by the wash solution.

Abstract: A nephelometer including an optical excitation system for directing light through a first window area into a cylindrical glass container and an optical detection system for quantitatively monitoring light scattered by a substance within the container and passing therefrom through a second window area. The optical detection system includes a lens system in optical alignment with the second window area and focused on an optical dark region on an inner wall of the container opposite the second window area. The optical dark region is free of internal light reflections. Therefore, the light monitored by the detection system is scattered light from the substance substantially free of internal light reflections representing background error.

Abstract: A signal conditioning circuit for extracting unipolar noise from an analog input signal by isolating the unipolar noise component and subtracting it from the input signal. The circuit includes a coupling capacitor receiving the analog signal and an ideal clamp connected to the capacitor output terminal to clamp the capacitor to an edge of the unipolar noise signal. The capacitor is thus prevented from charging toward a level representing an average value of the unipolar noise and hence functions to pass the noise undistorted for subtraction from the analog input signal. The clamp comprises an operational amplifier having a first input terminal connected to the capacitor output terminal and a second input terminal connected to a source of reference voltage. A diode is connected in a feedback path between an output terminal of the amplifier and the first input terminal thereof.

Abstract: A fluorometer for analyzing a sample by detecting light induced radiation emitted from the sample including apparatus for generating a narrow slit of light in the plane of the sample and transfer apparatus including a light shield having an acutely angled port immediately adjacent the sample for collecting radiation emitted by the sample and transmitting same via a light pipe to a remote detector.