Abstract: A variable pipette is disclosed which is so designed that its volumetric capacity for sucking and discharging a sample is variable. A first-stage stroke l.sub.1 for sucking and discharging a sample is defined between a first first-stage stop portion of a nut and a second first-stage stop portion of an actuating shaft, and this stroke l.sub.1 is set through the actuating shaft, a first stop portion of a threaded hollow shaft, the hollow shaft and the nut, not through any portion of the body of the pipette. Therefore, even if the temperature of the body is raised by the heat transmitted from the operator's hand as it grips the pipette and the body is thereby expanded axially, the above-described stroke l.sub.1 is independent of the expansion of the body and there is therefore hardly any error produced in the stroke l.sub.1.

Abstract: A repeating dispenser for dispensing uniform quantities of liquid includes an actuator rotatably connected to an actuating button. The actuator is biased upward by a spring towards a downwardly facing abutment in the non-actuated condition of the dispenser and is connected through a vertically displaceable rack shaft to a slide which releaseably mounts a cylinder piston device comprising a plurality of identical pistons and cylinders. An operating rod connects the slide to a suction button which is slideable along the outside surface of the dispenser. A pawl cooperates with the rack shaft and is kept from engagement with the rack shaft in the non-actuated condition of the dispenser. The actuating button includes a series of step-like stop portions engageable with an upwardly facing abutment to allow the repeated dispensing of uniform quantities of liquid.

Abstract: A pipette device adapted to removably mount a tip at its lower end and having a housing in which there are provided a cylinder chamber communicating with the interior of the mounted tip, a plunger adapted to operate in the cylinder chamber for sucking a liquid and then discharging the same, a direct current motor coupled to the plunger through a plunger driving mechanism, and a potentiometer for producing a voltage signal representing the position of the plunger, so that sucking and discharging of the liquid can be effected by detecting the voltage signal produced by the potentiometer and controlling the direction and amount of the rotation of the motor by the utilization of such detected voltage signal. Also disclosed is a control device for use with the pipette device including a servo system for receiving the voltage signal produced by the potentiometer as a feedback signal and a sequence circuit adapted to change the balance-point of the servo system in a preselected sequence.

Abstract: A pipetting device including a vertical cylinder provided on the lower end portion of a cylindrical housing, a piston working in the cylinder, an actuating rod connected to the piston and extending vertically through the housing, an operating knob mounted on the upper end of the actuating rod, a return spring biassing upwards the actuating rod, and a hollow tip mounted removably on the lower end of the cylinder for receiving liquid therein. The opposite ends of the return spring are connected non-rotatably to the housing and the actuating rod respectively thereby the actuating rod is biassed angularly with respect to the vertical axis thereof. The device further includes guiding mechanism for controlling the downward movement of the actuating rod in normal operating condition and allowing an additional downward movement thereof when the actuating rod is rotated angularly whereby the tip is removed off from the pipetting device.

Abstract: A pipetting device including a cylinder disposed at the lower end portion of a cylindrical housing, a piston working in the cylinder and having a piston rod secured thereto to extend through the housing, an actuating knob secured to the upper end of the piston rod, and a return spring biassing the piston rod upwardly, wherein the device further comprises a sleeve fitted screw-threadingly in the housing and engaging with the piston rod slidably but non rotatably, locking means releasably preventing rotation of the sleeve in the housing, an elongated transparent window having a scale thereon and being formed in the housing, and a datum line formed around the outer periphery of the sleeve.

Abstract: A pipetting apparatus comprising a housing, a liquid receiving tube attached to the lower end of the housing and receiving a predetermined amount of a liquid sample therein, a cylinder piston device disposed in the housing for applying vacuum pressure on the upper end of the liquid receiving tube for sucking a liquid sample into the tube, a manually operable device for actuating the cylinder piston device, an air inlet for directing compressed air into the housing, and a manually operable valve for directing compressed air either to the upper end of the liquid receiving tube or to atmosphere.