US 5,513,958 AGranted

Accumulator charging valve

AssigneeCaterpillar Inc.

InventorMichael J. Mientus

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Abstract

An accumulator charging valve has a first valve spool determining a cut-in pressure level at which fluid from a pump is directed to an accumulator and a second valve spool determining the cut-out pressure level at which fluid is no longer directed to the accumulator. When the pressure at the accumulator reaches a predetermined high level, the second valve spool moves to a position communicating an inlet port with an intermediate passage. The first spool is normally at a position blocking the intermediate passage from an outlet port so that a flow path is established through a pair of orifices reducing the pressure in the intermediate passage and the inlet port. The reduced pressure is transmitted to an actuating chamber to hold the second valve spool in the above noted position and to a pump displacement controller to destroke the pump to a low standby pressure displacement. When the pressure at the accumulator drops to a predetermined low level, the first valve spool moves to a position communicating the intermediate passage with the outlet port venting the actuating chamber so that the second valve spool moves to a position blocking the inlet port from the intermediate passage. This increases the pressure directed to the displacement controller upstroking the pump to a high pressure displacement. The cycle is repeated when the pressure reaches the predetermined high level.

Claims8

Dependent claims

An accumulator charging valve comprising:

a body having an inlet port, an orifice disposed in the inlet port, an outlet port, an intermediate passage, an orifice communicating the intermediate passage with the outlet port, and a control port;
a first valve spool slidably disposed in the body and having a first position establishing communication between the intermediate passage and the outlet port and a second position blocking the intermediate passage from the outlet port;
a second valve spool slidably disposed in the body and having a first position blocking the inlet port from the intermediate passage and a second position establishing communication between the inlet port and the intermediate passage;
a first spring device resiliently biasing the first spool to the first position and having a predetermined preload thereon when the first valve spool is at the first position;
a second spring device resiliently biasing the second valve spool to its first position and having a predetermined preload thereon when the second valve spool is at the first position;
first piston means for moving the first valve spool to its second position when the fluid pressure in the control port reaches a first predetermined level;
second piston means for moving the second valve spool to its second position when the fluid pressure in the control port reaches a second predetermined level which is higher than the first predetermined pressure level;
and
an actuating chamber defined at one end of the second valve spool and being in continuous communication with the intermediate passage.

6 more elements

Dependencies are inferred from the claim text.