Abstract: A hydraulic booster unit and system for use in operating hydraulic units, such as work holding hydraulic cylinders, from a compressed air power source is disclosed. The booster includes a unique refill unit that automatically feeds hydraulic fluid from a reservoir to the booster to replace lost fluid during use, and also includes an alerter for giving warning on the onset of a low fluid condition (such as may occur from an exhausted reservoir or excessive leak), and thus protects against excessive leakage as well as the dangers to the work piece and worker inerent in a low fluid condition. The alerter may be a visual unit or a compressed air-operated audible alarm or both.

Abstract: In a hydraulic brake system, a housing includes a brake master cylinder and a reservoir formed therein for containing a supply of brake fluid. A sensor piston in contact with the pressure in the brake master cylinder is connected to an indicator piston. The indicator piston is coaxial with a blind cylindrical indicator bore. The blind bore and indicator piston are in communication with the reservoir at a level below which the brake fluid should not be allowed to recede. When the brake is operated, brake master cylinder pressure urges the sensor piston outward. The connected indicator piston is urged toward the blind bore. If the reservoir contains fluid, the blind bore is filled with the fluid. Fluid lock of the indicator piston therefore occurs before any appreciable indicator piston motion into the blind indicator bore. On the other hand, if the reservoir, and the communicating indicator bore, are empty, the indicator piston is enabled to enter the indicator bore by compressing air therein.

Abstract: The reservoir includes a housing, a separating wall in the housing in the transverse direction of the vehicle to provide two chambers, each of the two chambers being divided by a partition in the longitudinal direction of the vehicle into a large and a small chamber compartments. The two chambers are interconnected by a first port in the partition of one of the two chambers spaced from the separating walls interconnecting the large and small chamber compartments of the one of the two chambers, the small chamber compartment of the one of the two chambers, a second port in the separating wall interconnecting the small chamber compartment of the one of the two chambers with the small chamber compartment of the other of the two chambers and a third port in the partition of the other of the two chambers spaced from the separating wall interconnecting the large and small chamber compartments of the other of the two chambers.

Abstract: In a combined reservoir made of a plastic material such as nylon or polythene and master cylinder housing assembly, a bolt is screwed into coaxial openings of the housing and the reservoir to fasten each other. A metallic sleeve is secured to the opening of the plastic reservoir to limit the compression of plastic reservoir when the bolt is rotated. Thus, a seal rubber provided between the plastic reservoir and the housing is properly compressed to make effectively fluid-tight therebetween due to a proper fastening force exerted on the metallic sleeve.