US 6,293,099 B1 · Hydraulic circuit for forklift

Abstract

This invention relates to a hydraulic circuit for a forklift, and intends to lift a fork for lifting in high speed, or to inch the fork little by little, as occasion demands. In this hydraulic circuit, a first electric motor for driving a first electric motor disposed on a first route extending from a tank to a lift cylinder is on-off controlled. A check valve disposed on the first route downstream of the first hydraulic pump allows only an oil-flow from the oil tank to the lift cylinder. A second motor for driving a second electric motor disposed on a second route extending from a tank to a lift cylinder is PMW-controlled. A flow controlling valve is disposed on the second route downstream of the second hydraulic pump and including an electro-magnetic valve operated associating with the PMW-controlling of said second electric motor. A separating element hydraulically separates the check valve and the electro-magnetic valve of the flow controlling valve.

Claims13

Dependent claims

A hydraulic circuit for supplying an oil from an oil tank to at least a lift cylinder for lifting a fork for lifting, comprising:

a first route extending from the oil tank to the lift cylinder;
a first hydraulic pump disposed on said first route;
a first electric motor on-off controlled for driving said first hydraulic pump;
a first check valve disposed on said first route downstream of said first hydraulic pump for allowing only an oil-flow from the oil tank to the lift cylinder;
a second route extending from the oil tank to the lift cylinder;
a second hydraulic pump disposed on said second route;
a second electric motor PWM controlled for driving said second hydraulic pump;
a flow controlling valve disposed on said second route down stream of said second hydraulic pump and including an electro-magnetic valve operated associating with the chopper-controlling of said second hydraulic motor;
and
separating means for hydraulically separating said check valve and said electro-magnetic valve of said flow controlling valve.

7 more elements

Dependencies are inferred from the claim text.

Hydraulic circuit for forklift

Life of this patent

Hydraulic circuit for forklift

Life of this patent

Abstract

Claims13