Material or article handling – Elevator or hoist and loading or unloading means therefor – Comprising means enabling additional movement of carrier or...
Patent
1980-04-07
1983-07-12
Reeves, Robert B.
Material or article handling
Elevator or hoist and loading or unloading means therefor
Comprising means enabling additional movement of carrier or...
414671, B66F 906
Patent
active
043927726
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates generally to load carrying apparatus and more particularly to a load lifting carriage having side shift adjustable forks.
2. Background Art
Material handling vehicles such as fork lift trucks are used to pick up and deliver loads between stations. The fort lift truck typically has a mast which supports a load lifting carriage that can be raised along the mast. The carriage normally carries a pair of forks which are maneuverable beneath the load prior to lifting the load.
For a variety of well-known reasons, it is desirable to be able to displace the forks laterally along the carriage in relation to the centerline of the carriage and hence the truck. For example, as the truck approaches the load the forks may not be properly aligned with the load to be maneuvered under it. Rather than maneuvering the entire truck, it may be preferable to reposition the forks along the carriage. Under certain loading conditions, it may be necessary that the pair of forks be on the same side of the centerline of the carriage.
In one type of carriage and fork arrangement, the carriage is fixed on the mast against lateral displacement. The forks are releasably secured by pins in notches on the top edge of the carriage and can be laterally displaced along the carriage by removing the pins and manually positioning them into other notches. One problem is that the forks, being heavy and cumbersome, may require significant manual exertion in repositioning them along the carriage.
In another type of carriage and fork arrangement, the forks can be hydraulically laterally displaced in relation to the centerline. Typically, the carriage includes a main carriage which is fixed on the mast against a lateral displacement and a sub-carriage which is movable laterally along the main carriage. The forks are mounted on the sub-carriage and hydraulic cylinders are connected to the sub-carriage to shift it laterally along the main carriage. One problem with this arrangement is that the sub-carriage cannot be shifted laterally so as to position both forks on one side of the centerline. Furthermore, the member which is shiftable to laterally displace the forks, i.e., the sub-carriage, is a member that supports the forks and hence the load being carried by the forks. Consequently, for a given load carrying capacity, this sub-carriage must be of a heavyweight construction. This adds to the overall weight of the mast assembly, which reduces the actual load carrying capacity of the lift truck. Also, because of the sub-carriage, the forks and hence the load are positioned further away from the front wheels of the truck, which undesirably increases the load moment constant.
Furthermore, the cylinder rods of the cylinders are rigidly connected to the members that are shifted to laterally displace the forks. Should, for example, an undue side impact load act on the carriage or forks, this can be transmitted to the rods and bend or otherwise damage them.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a load lifting carriage is provided having rails, first and second forks movably supported on the rails, a pair of opposite spaced apart sides, first and second cylinders connected to the carriage and a vertical carriage centerline. Included are first means for coupling the first cylinder to the first fork at first and second longitudinal locations relative to the first cylinder and second means for coupling the second cylinder to the second fork at third and fourth longitudinal locations relative to the second cylinder, the first fork is movable in response to movement of the first cylinder to either a location past the centerline or to a location closely adjacent one of the sides, and the second fork is movable in response to movement of the second cylinder to either a location closely adjacent the other side or to a location past the centerline.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG
REFERENCES:
patent: 2270664 (1940-11-01), Weaver
patent: 2663443 (1953-12-01), Schenkelberger
patent: 2822101 (1958-02-01), Schenkelberger
patent: 3241698 (1966-03-01), Krett
patent: 3684113 (1972-08-01), Roller
patent: 3754673 (1973-08-01), Barda et al.
patent: 4002256 (1977-01-01), Kroboth
patent: 4125199 (1978-11-01), Abels et al.
Hickman Alan J.
Hubbuch David F.
Reeves Robert B.
Towmotor Corporation
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