Abstract: A controlled volume liquid meter comprises a liquid metering chamber defined between a rigid wall and an opposed flexible membrane wall. Inlet and outlet ports are positioned adjacent the ends of the chamber with the ports defining paths of liquid flow therethrough which are transverse to the direction of liquid flow in the chamber. A pair of plunger members are provided, along with apparatus for alternatingly pressing the plunger members against the membrane wall and inserting the plunger members into the inlet and outlet ports to alternatingly open and close them. In accordance with this invention, the plunger members permit variation of the length of each plunger member, with a spring urging the plunger members to occupy their maximum lengths. As a result of this, the force with which the plunger members press against the membrane wall is limited to a value governed by the spring.

Abstract: An electromagnetic switch which comprises an armature pivotally movable between first and second pivotal positions about a fulcrum positioned between its ends. Magnet means are positioned adjacent each of the armature ends and present opposite polarities outwardly from each end of the armature. Electromagnet core means define arms positioned adjacent the magnet means at each armature end, with the magnet means being each respectively movable toward and away from an arm when pivoting between the first and second pivotal positions. The armature can be moved between the first and second positions by changing the polarity of the electromagnet core means. In accordance with this invention, restraining means engagable with the armature for preventing the armature from pivoting into contact with the electromagnet core means are provided for prevention of noise and for preservation of the life of the magnet means.

Abstract: Flow controlling apparatus for the administration of parenteral solutions or the like includes a casette in a controller member adapted to receive and hold the casette. In accordance with this invention, means are provided for indicating the correct position of the casette in the controller member.

Abstract: A system for infusing fluids into the human body includes a peristaltic-type metering apparatus which controls the flow of fluid through a disposable administration set. The metering apparatus includes a control system which allows the volume and rate of flow of the fluid to be infused to be accurately preset by the operator. The control system provides an alarm function in the event of malfunction of the pump or occlusion of the tubing of the administration set, and a minimum pumping rate for maintaining fluid flow through a system after the desired volume of fluid has been infused. Novel power supply circuitry within the control system renders the system immune to power line transients, and a novel bubble detector circuit provides for more reliable detection of air bubbles in the tubing.