초록 ▼

A high-pressure source of hydraulic fluid and a sump are connected to a cyclically operating user of hydraulic fluid having a hydraulic accumulator by a high-pressure feed line having one end connected to the source and an opposite end connected to the accumulator and user. A pressure-limiting valve

A high-pressure source of hydraulic fluid and a sump are connected to a cyclically operating user of hydraulic fluid having a hydraulic accumulator by a high-pressure feed line having one end connected to the source and an opposite end connected to the accumulator and user. A pressure-limiting valve has an input side connected to the high-pressure line between the ends thereof and an opposite output side connected to the sump. This valve opens only when pressure in the line exceeds a preset maximum to allow flow between its sides. A detector is connected to the output side of the valve for measuring the peak pressure thereof over several operating cycles of the user and a controller is connected to the detector for operating when the peak pressure detected over several operating cycles exceeds a predetermined threshold.

대표청구항 ▼

In combination with: a high-pressure source of hydraulic fluid having an output at a generally constant intermediate pressure; a sump; a cyclically operating user of hydraulic fluid; a hydraulic accumulator at the user; a high-pressure feed line having one end connected to the output of the source a

In combination with: a high-pressure source of hydraulic fluid having an output at a generally constant intermediate pressure; a sump; a cyclically operating user of hydraulic fluid; a hydraulic accumulator at the user; a high-pressure feed line having one end connected to the output of the source and an opposite end connected to the accumulator and user; a pressure-limiting valve having an input side connected to the high-pressure line between the ends thereof and an opposite output side, the valve opening only when pressure in the line exceeds a preset maximum to allow flow between its sides; and a drain conduit connected between the output side and the sump; the improvement comprising: a restriction in the drain conduit, a pressurizable compartment, a branch line having one end connected to the drain conduit between the restriction and the output side and an opposite end opening into the compartment, a check valve connected between the compartment and the opposite end of the branch line and only permitting fluid flow into the compartment, and switch means actuatable when the volume in the compartment exceeds a predetermined threshold.