Robert P Karvonen

US Patent:

49647806, Oct 23, 1990

Filed:

Jan 11, 1988

Appl. No.:

7/142548

Inventors:

Robert Karvonen - Pelkie MI

International Classification:

B66C 2300

US Classification:

414728

Abstract:

A direction controlling mechanism for an extendible boom forklift or the like controls the direction of movement of a predetermined point, such as a fork section connected to the distal end of the boom sections, relative to the forklift frame during retraction or extension of the boom members. The direction controlling mechanism is disposed between the proximal end of the boom sections and the main frame section of the forklift. The direction controlling mechanism includes an extendible member disposed between an upper shaft provided on the boom sections and a lower shaft provided on the vehicle frame. The length of the extendible member can be fixed during retraction or extension of the booms, and a driving mechanism moves the fixed length extendible member along the upper and lower shafts. Such movement tends to compress or elongate the extendible member, and the tendency of the extendible member to compress or elongate is sensed by a sensing mechanism and translated into hydraulic fluid pressure, which is directed to the appropriate side of the boom lift cylinders so as to maintain the load carried by the boom at a constant predetermined direction of movement during extension or retraction of the boom members. In a preferred embodiment, the load is maintained at a constant elevation relative to the forklift frame.