Log grapple device
AssigneeTimberjack Inc.
InventorJohn A. McCutcheon
Life of this patent
Estimating the term…
Abstract
A hydraulic system (10) for a log grapple device (12), including an unloader valve (20) and an accumulator (22) located downstream of a control valve (18) which determines the direction of fluid flow to the actuating cylinder (108) controlling the opening and closing of the grapple device. When a predetermined operating pressure is reached the unloader valve diverts outlet flow from a pump (16) to a reservoir (14) and isolates the system downstream of the unloader valve, the accumulator maintaining pressure on the grapple device. When the grapple device is to be opened, a pilot check valve assembly (60) within the unloader valve permits reverse flow through the unloader valve.
Claims6
In a log grapple device comprising a pair of tongs mounted for movement toward and away from one another, and at least one hydraulic cylinder connected to said tongs and operable to move said tongs toward and away from one another;
- a hydraulic circuit for supplying pressurized hydraulic fluid to said cylinder;
- said hydraulic circuit comprising a reservoir;
- a pump;
- a control valve connected between said pump and said cylinder and operable to selectively apply hydraulic fluid to a first side of said cylinder for moving said tongs toward one another and to a second side of said cylinder for moving said tongs away from one another;
- an unloader valve assembly connected between said control valve and said first side of said cylinder, said unloader valve assembly being operable to direct flow from said pump to said reservoir and prevent flow from said first side through said unloader valve when a predetermined pressure is applied to said first side upon closing of said tongs upon a load grasped therein;
- and an accumulator connected between said unloader valve assembly and said first side and operable to maintain hydraulic pressure on said first side if said tongs close further upon shifting of the load grasped therein.
Dependencies are inferred from the claim text.