Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1982-03-22
1984-04-10
Rolla, Joseph J.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
187 9E, 308 3B, B66B 702
Patent
active
044415850
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a lift mast assembly and more particularly to a lift mast assembly having a moveable upright mounted on a fixed upright and elevationally extensibly movable relative thereto and a lift jack mounted on said lift mast assembly at a location between the fixed and movable uprights.
2. Background Art
Lift mast assemblies for use on a vehicle such as a lift truck are well known in the art. Such lift masts typically have a fixed pair of spaced apart uprights which are pivotally mounted on the lift truck and a movable pair of spaced apart uprights mounted on the fixed pair of uprights and elevationally extensibly movable relative thereto and a carriage mounted on the movable uprights and elevationally movable relative to the movable uprights. A lift jack is operatively connected between the fixed and movable uprights and carriage for effecting selective elevational movement of the movable uprights and the carriage.
In the past the lift jack was mounted on the lift mast at a centered location between the fixed pair of uprights which reduced the lift truck operator's field of visibility making accurate handling of material quite difficult. Further, the addition of lift chains and sheaves which are associated with the lift cylinder reduced the visibility to a greater degree.
Recent attempts have been made by industry to improve the operator's visibility and thereby improve efficiency and accuracy of operation. These attempts primarily consisted of locating the lift cylinder(s) outboard, behind, or in front of the uprights which would remove the obstruction caused by the cylinder from the center of the mast. Examples of these cylinder locations are shown in U.S. Pat. Nos. 3,127,956 dated Apr. 7, 1964 to H. W. Hosbein et al; 4,030 ,568 dated June 21, 1977 to Lloyd K. Heinold and U.S. Pat. No. 4,219,302 dated Aug. 26, 1980 to Edward V. Leskovec. Although these solutions have improved the visibility they have not totally solved this or related problems. In mast assemblies where the lift jacks are mounted behind the uprights it is necessary to locate the mast a greater distance from its mounting on the lift truck to provide clearance between the cylinders and the lift truck and therefore the load moment characteristic of the vehicle is changed which reduces the load carrying capacity of the machine. Likewise, placing the lift jacks in front of the uprights requires the load engaging carriage to be moved further away from the uprights of the lift mast thereby moving the load engaging carriage and a load to be supported thereon further away from the vehicle which also changes the load moment relationship which results in reduced lift capacity of the vehicle. Placement of the lift cylinders outboard of the uprights of the lift mast requires the uprights located adjacent one side of the vehicle to be moved inward and closer to the uprights located adjacent the other side of the vehicle as they are preferably located between the vehicle wheels which are at a fixed maximum width. Therefore, the mast uprights are now closer together which reduces the space provided between the uprights resulting in reduction in the operator's visibility. Attempts have been made to minimize this problem by reducing the length of the lift cylinders and locating them outboard of the outer fixed uprights and over the wheels. This, however, reduces the overall lift height of the lift mast assembly for a given upright length due to the reduction and stroke of the lift cylinders.
Often the lift jacks for the lift mast are nested between the inner or movable uprights. When a pair of lift cylinders are utilized they are each normally located closely adjacent a respective one of the movable uprights. Such an arrangement is shown in U.S. Pat. No. 2,456,320 dated Dec. 14, 1948 to E. P. Repke.
Lift chain and sheave arrangements are usually provided to connect the carriage and/or lift mast assembly to the lift jacks to effect elevational movement of the uprights and/or the carriage in response to movem
REFERENCES:
patent: 2456320 (1948-12-01), Repte
patent: 3127956 (1964-04-01), Hosbein et al.
patent: 4030568 (1977-06-01), Heinold
patent: 4219302 (1980-08-01), Leskovec
patent: 4238004 (1980-12-01), Olson
Hickman Alan J.
Noland Kenneth
Rolla Joseph J.
Towmotor Corporation
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