Forklift apparatus for unloading articles from an elevated surface

Apparatus for unloading articles from an elevated surface, comprising:

• a frame;
• frame support means for movably supporting said frame on a support surface lower than said elevated surface;
• drive means for propelling said frame along said support surface;
• article-engaging means for liftingly engaging an article resting on said elevated surface and to be removed and lowered therefrom;
• linkage means, carried by said frame for movement therewith, for interconnecting said frame and said article-engaging means, said linkage means being extendable and retractable in horizontal and vertical directions;
• actuating means for moving said linkage means relative to said frame to permit said article-engaging means to be brought into lifting engagement with the article, and then move said article-engaging means to remove and lower the article from said elevated surface;
• and
• anti-tipping means for preventing load-caused tipping of said apparatus by sensing a tipping load moment imposed on said apparatus by an article carried by said article-engaging means, said tipping load moment being less than that required to tip said apparatus, and responsively preventing said actuating means from moving said linkage means in a manner substantially increasing said tipping load moment,
• said anti-tipping means including anti-reverse means for automatically preventing said apparatus from being backed away from said elevated surface when the sensed tipping load moment on said apparatus is at or above a predetermined level.

A forklift device for unloading articles from an elevated surface, comprising:

• a frame;
• frame support means for movably supporting said frame on a support surface lower than said elevated surface;
• drive means for propelling said frame along said support surface;
• fork means for liftingly engaging an article resting on said elevated surface;
• articulated linkage means, carried by said frame for movement therewith, for interconnecting said frame and said fork means, said articulated linkage means being movable relative to said frame between a first, fully raised and extended position and a second, fully lowered and retracted position and including a gantry structure pivotally connected to said frame, and a boom structure pivotally interconnected between said gantry structure and said fork means;
• and
• actuating means for selectively and independently pivoting said gantry structure relative to said frame, said boom structure relative to said gantry structure, and said fork means relative to said boom structure, to horizontally, vertically and pivotally position said fork means so that the same may be lifted to a level above that of said elevated surface, moved toward and into lifting engagement with the article, and lifted and lowered from said elevated surface to remove the article therefrom, said actuating means being further operable to simultaneously pivot said gantry structure relative to said frame, said boom structure relative to said gantry structure, and said fork means relative to said boom structure, to selectively move said articulated linkage means between said first and second positions thereof while automatically maintaining said fork means in a predetermined, fixed pivotal orientation relative to said support surface, said, actuating means including:
• first hydraulic cylinder and actuating rod means interconnected between said frame and said gantry structure and being drivable to cause pivotal motion of said gantry structure in a selected direction relative to said frame,
• second hydraulic cylinder and actuating rod means interconnected between said frame and said boom structure and being drivable to cause pivotal motion of said boom structure in a selected direction relative to said gantry structure,
• third hydraulic cylinder and actuating rod means interconnected between said boom structure and said fork means and being drivable to cause pivotal motion of said fork means in a selected direction relative to said boom structure, and
• hydraulic actuation circuit means for flowing hydraulic fluid from a source thereof through said first, second and third hydraulic cylinder and actuating rod means to operatively drive the same, said hydraulic actuation circuit means including:
• a first circuit portion independently operable to flow hydraulic fluid through said first hydraulic cylinder and actuating rod means,
• a second circuit portion independently operable to flow hydraulic fluid through said second hydraulic cylinder and actuating rod means,
• a third circuit portion independently operable to flow hydraulic fluid through said third hydraulic cylinder and actuating rod means, and
• a fourth circuit portion independently operable to simultaneously flow selectively proportioned amounts of hydraulic fluid through said first, second and third hydraulic cylinder and actuating rod means to synchronize in a predetermined manner the pivotal motions of said gantry structure, said boom structure and said fork means during the resultant movement of said articulated linkage means,
• said first circuit portion including a first pair of hydraulic lines operatively connected to said first hydraulic cylinder and actuating rod means, and first three-position direction control valve means operable to control the flow of hydraulic fluid through said first pair of hydraulic lines,
• said second circuit portion including a second pair of hydraulic lines operatively connected to said second hydraulic cylinder and actuating rod means, and second three-position directional control valve means operative to control the flow of hydraulic fluid through said second pair of hydraulic lines,
• said third circuit portion including a third pair of hydraulic lines operatively connected to said third hydraulic cylinder and actuating rod means, and third three-position directional control valve means operable to control the flow of hydraulic fluid through said third pair of hydraulic lines, and
• said fourth circuit portion including fourth, fifth and sixth pairs of hydraulic lines operatively communicated with said first, second and third hydraulic cylinder and actuating rod means, respectively, a seventh pair of hydraulic lines for flowing hydraulic fluid through said fourth, fifth and sixth pairs of hydraulic lines, fourth three-position directional control valve means for controlling the flow of hydraulic fluid through said seventh pair of hydraulic lines, and adjustable flow dividing means, interconnected between said seventh pair of hydraulic lines and said fourth, fifth and sixth pairs of hydraulic lines, for adjustably regulating the relative hydraulic fluid flow rates through said fourth, fifth and sixth pairs of hydraulic lines.

A forklift device positionable on a support surface adjacent an elevated surface and adapted to reach above and a substantial distance across said elevated surface, liftingly engage an article resting thereon, and remove and lower the article from said elevated surface, said forklift device comprising:

• a frame;
• frame support means for movably supporting said frame on said support surface;
• drive means for propelling said frame along said support surface;
• fork means for liftingly engaging the article;
• articulated linkage means, carried by said frame for movement therewith, for interconnecting said frame and said fork means, said articulated linkage means being movable relative to said frame between a first, fully raised and extended position and a second, fully lowered and retracted position and including a gantry structure pivotally connected to said frame and having an outer end portion, and an elongated boom structure having an inner end pivotally connected to said gantry structure and an outer end pivotally connected to said fork means;
• actuating means operable to control the movement of said articulated linkage means and said fork means, said actuating means including:
• first hydraulic cylinder and actuating rod means interconnected between said frame and said gantry section and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said gantry structure in a selected direction relative to said frame,
• second hydraulic cylinder and actuating rod means interconnected between said frame and a longitudinally intermediate portion of said boom section and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said boom structure in a selected direction relative to said gantry structure,
• third hydraulic cylinder and actuating rod means interconnected between said boom structure and said fork means and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said fork means in a selected direction relative to said boom structure, and
• hydraulic circuit means for supplying hydraulic fluid from a source thereof to said first and second internal cylinder portions of said first, second and third hydraulic cylinder and actuating rod means;
• control means operative to control hydraulic fluid flow through said hydraulic circuit means to said first and second internal cylinder portions of said first, second and third hydraulic cylinder and actuating rod means to selectively and independently cause pivotal motion in a selected direction of said gantry structure relative to said frame, said boom structure relative to said gantry structure, and said fork means relative to said boom structure;
• anti-tipping means for preventing load-causing tipping of said device by sensing a tipping load moment imposed on said device by an article carried by said fork means, said tipping load moment being less than that required to tip said device, and responsively preventing said actuating means from moving said articulated linkage means in a manner substantially increasing said tipping load moment;
• and
• anti-reverse means for preventing said drive means from being utilized to back said device away from said elevated surface when the sensed tipping load moment is at or above a predetermined level.

A forklift device positionable on a support surface adjacent an elevated surface and adapted to reach above and a substantial distance across said elevated surface, liftingly engage an article resting thereon, and remove and lower the article from said elevated surface, said forklift device comprising:

• a frame;
• frame support means for movably supporting said frame on said support surface;
• drive means for propelling said frame along said support surface;
• fork means for liftingly engaging the article;
• articulated linkage means, carried by said frame for movement therewith, for interconnecting said frame and said fork means, said articulated linkage means being movable relative to said frame between a first, fully raised and extended position and a second, fully lowered and retracted position and including a gantry structure pivotally connected to said frame and having an outer end portion, and an elongated boom structure having an inner end pivotally connected to said gantry structure and an outer end pivotally connected to said fork means;
• actuating means operable to control the movement of said articulated linkage means and said fork means, said actuating means including:
• first hydraulic cylinder and actuating rod means interconnected between said frame and said gantry section and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said gantry structure in a selected direction relative to said frame,
• second hydraulic cylinder and actuating rod means interconnected between said frame and a longitudinally intermediate portion of said boom section and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said boom structure in a selected direction relative to said gantry structure,
• third hydraulic cylinder and actuating rod means interconnected between said boom structure and said fork means and having first and second internal cylinder portions for receiving hydraulic fluid to cause pivotal motion of said fork means in a selected direction relative to said boom structure,
• hydraulic circuit means for supplying hydraulic fluid from a source thereof to said first and second internal cylinder portions of said first, second and third hydraulic cylinder and actuating rod means;
• control means operative to control hydraulic fluid flow through said hydraulic circuit means to said first and second internal cylinder portions of said first, second and third hydraulic cylinder and actuating rod means to selectively and independently cause pivotal motion in a selected direction of said gantry structure relative to said frame, said boom structure relative to said gantry structure, and said fork means relative to said boom structure;
• roller means, movable with said articulated linkage means, for engaging said elevated surface and rollingly supporting thereon the weight of an article carried by said fork means;
• and
• deactivating means operable to prevent said second hydraulic cylinder and actuating rod means from vertically supporting said boom structure during engagement of said roller means with said elevated surface.