Implements or apparatus for applying pushing or pulling force – Hoisting truck – Single throw lever
Patent
1992-09-24
1993-04-13
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Hoisting truck
Single throw lever
B60P 148
Patent
active
052014940
ABSTRACT:
A hydraulic jack includes a linkage movable from a first position to a second position for engaging and elevating a load, a hydraulic ram coupled to the linkage for moving the same toward its second position upon the application of fluid pressure, and a pump coupled to the hydraulic ram for applying fluid pressure thereto. The pump includes a piston operable for delivering a first quantity of hydraulic fluid to the ram through a first path at a first pressure and a second quantity of hydraulic fluid to the ram through a second path at a second pressure, the first quantity being substantially larger than the second quantity and the first pressure being substantially lower than the second pressure. A pressure relief valve is coupled to the first path for venting the same when the back pressure from the hydraulic ram exceeds a predetermined value whereby the linkage is advanced at a first, higher speed from its first position to engagement with the load and at a second, lower speed but with increased force after the load has been engaged for elevating the same.
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