Abstract: An apparatus for the operation of a working element of an excavator. An arm connected to the working element and a boom for supporting and operating the arm are fabricated each in the shape of a hollow tube whose opposite ends are left unclosed. A boom cylinder, an arm cylinder, or a working element cylinder is disposed as contained within the boom or the arm. The point of connection of the boom to the arm and the point of connection of the working element cylinder to the arm constitute a joint fulcrum. The point of connection of the boom cylinder to the boom and the point of connection of the arm cylinder to the boom similarly constitute a joint fulcrum.

Abstract: Braking system for use in track-type vehicles. The system includes a steering brake, a brake cylinder in which an emergency brake piston and a spring for biassing the emergency brake piston to its braking position are provided. The emergency brake piston is operatively connected to the steering brake through a link mechanism and defines with the braking cylinder a hydraulic pressure receiving chamber connected to a hydraulic fluid supply source to maintain the emergency brake piston in its non-braking position against a biassing action of the spring in case of the normal condition of the vehicle. The link mechanism comes into contact with an auxiliary lever serving to move the emergency brake piston to its non-braking position.