US 4,731,999 A · Power transmission

Abstract

A hydraulic system comprised of a pump, a first valve in the inlet to the pump, and a second valve which activates or deactivates a third valve which permits the loading and unloading of the pump discharge. A motor is provided to operate the first valve for opening or closing the pump inlet. This motor also actuates the second valve in concert with the operation of the first valve to open or close a vent port to the third valve which opens or closes the passage from the pump discharge to tank, located away from the pump inlet. This permits unloading the pump discharge during the restriction of the pump inlet and allows the loading of the pump discharge after the opening of the pump inlet. With the pump inlet restricted, the system provides a low restrictive passage for circulating the prescribed small volume of flow used to lubricate and cool the pump.

Claims14

Dependent claims

A hydraulic system comprising

a pump having a discharge circuit,
a first valve in the inlet to the pump for restricting the flow into the pump when the first valve is closed,
a second valve,
a third valve in the discharge circuit for unloading the pump discharge circuit away from the pump inlet,
said second valve being operable to vent said third valve to tank pressure,
a motor for operating the first valve such that the pump inlet will be opened or be restricted and such that the second valve will open or be restricted to vent the third valve.

3 more elements

A hydraulic system comprising

a pump having an inlet and an outlet,
a first line from the outlet of the pump,
a normally closed inlet valve having an inlet and outlet controlling flow from a source to the inlet of said pump,
a normally closed unloading valve having an inlet connected to the first line and having an outlet,
a second line connected to the outlet of said unloading valve,
said unloading valve having means forming a restricted passage permitting flow from the first line to the second line,
a normally open vent valve having an inlet connected to the second line and having an outlet,
a third line extending from said outlet to said vent valve to the inlet valve,
a motor for moving said vent valve and said inlet valve to open positions,
said inlet valve having means for directing a predetermined amount of fluid to the inlet of the pump when the inlet valve is closed such that when the inlet valve is normally closed only said predetermined flow will occur for cooling and lubricating the pump and when there is no load on the system and the motor is operated to open the inlet valve, the inlet valve is opened and the vent valve is closed, the inlet valve, unloading valve and vent valve being constructed and arranged such that when there is a load on the hydraulic system and the motor is operated to open the inlet valve, the vent valve remains open before the inlet valve is completely opened providing communication between the unloading valve and tank pressure through the second line and the vent valve and thereby causing a pressure differential across the first line, the unloading valve and second line to open the unloading valve to discharge the flow from the first line to tank pressure until the inlet valve is fully open and the vent valve is closed.

7 more elements

Dependencies are inferred from the claim text.

Power transmission

Life of this patent

Power transmission

Life of this patent

Abstract

Claims14