Abstract: A high performance, multiple rotor, hydraulically driven riding trowel for finishing concrete includes a rigid trowel frame with two or more downwardly-projecting, bladed rotor assemblies that frictionally engage the concrete surface. The rotor assemblies are tilted with double acting hydraulic cylinders to effectuate steering and control. Double acting hydraulic cylinders also control blade pitch. Hydraulic pressure to the rotors is monitored and controlled by an unloader valve system that monitors drive pump pressure with a shuttle valve to derive an unloader pilot signal. A sequence valve responds to the unloader pilot signal to control a pressure valve that bypasses the normal foot control valve in an overpressure situation. The pressure control head signal normally applied to the hydraulic drive motor control heads is modified with a feedback signal to automatically control the associated pump swash plates.

Abstract: A high performance, multiple rotor, hydraulically driven riding trowel for finishing concrete includes a rigid trowel frame with two or more downwardly-projecting, bladed rotor assemblies that frictionally engage the concrete surface. The rotor assemblies are tilted with double acting hydraulic cylinders to effectuate steering and control. Double acting hydraulic cylinders also control blade pitch. Hydraulic pressure to the rotors is monitored and controlled by an unloader valve system that monitors drive pump pressure with a shuttle valve to derive an unloader pilot signal. A sequence valve responds to the unloader pilot signal to control a pressure valve that bypasses the normal foot control valve in an overpressure situation. The pressure control head signal normally applied to the hydraulic drive motor control heads is modified with a feedback signal to automatically control the associated pump swash plates.

Abstract: A fluid layering device for use with a syringe to facilitate layering a liquid from the syringe onto a denser liquid contained in an open-top centrifuge tube. A fitting in the device is releasably attachable to the syringe for receiving liquid therefrom. An elongate nozzle carried on the fitting has a pair of opposed end faces, and a pair of flow-constricting bores communicating associated nozzle end faces with liquid received in the fitting. An annular step formed on the fitting is engageable by friction fit with the tube's upper open end to hold the nozzle at an axially aligned position within the tube. At this position, each of the nozzle end faces confronts, and is spaced from, an inner wall portion in the tube by a clearance which is adapted to produce, with liquid being forced from the syringe through the associated bore in the nozzle, a controlled-flow ribbon of liquid down the wall of the tube onto the upper surface of the denser liquid in the tube.

Abstract: An arrangement for controlling of carburation for an internal combustion engine in which the constriction to draw fuel into the air stream is controlled by a mechanism which controls the position of the constricting members proportionately to the speed of the output of the engine. The fuel supply is also controlled in proportion to the degree of constriction.