Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1980-10-03
1982-12-28
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
414635, 254386, B66B 920
Patent
active
043656935
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The invention relates to load moving devices such as mast assemblies. More particularly, the invention relates to such devices using a pair of lifting elements to elevate the load.
2. Background Art
In the use of apparatus for lifting or moving loads, it is desirable to have high visibility through or about the structure while utilizing a simple and inexpensive design. For example, a common application of such apparatus is as the mast assembly for a fork lift truck or other material handler. The mast assembly generally contains two fixed uprights attached to the vehicle with a movable upright mounted on each of the fixed uprights by rollers. A carriage carrying load engaging forks is mounted for movement on the movable uprights. The movable uprights and carriage can be selectively elevated to retrieve or place loads as desired.
In such mast assemblies forward visibility of the operator is necessarily restricted by the uprights and carriage. Design involved in the addition of hydraulic jacks and chains which control the actual movement of the uprights and carriage is therefore critical, in that it is undesirable to further restrict the visibility or to add additional complicated structure or weight to the vehicle. One common solution for maintaining visibility between the uprights is to incorporate two hydraulic jacks each of which is positioned closely to one set of the movable and fixed uprights to minimize further interference with forward visibility. Such practices and one such solution are discussed in U.S. Pat. No. 2,456,320 which issued to E. P. Repke on Dec. 14, 1948. Another solution, utilizing only two hydraulic jacks, is disclosed in U.S. Pat. No. 4,030,568 which issued to L. K. Heinold on June 21, 1977.
It will be apparent that using two cooperating spaced-apart hydraulic jacks does create additional problems in that with an unevenly loaded carriage the jacks will experience unequal loading. Thus, if the jacks are rigidly and separately mounted to the frame or fixed uprights there will be undesirable bending or side loads on the jacks and uneven loading of the chains as the jacks extend toward the end of full travel.
Maneuverability of the vehicle can also be affected by the elevation of the movable uprights, which can be of particular importance while the lift truck is being driven to a storage location. If the movable uprights extend above the height of the fixed uprights, it will be understood that driving a vehicle where there is low clearance, such as through doorways, can result in interference with the movable uprights. Thus, it is desirable in a mast assembly to have free lift, which allows the carriage to be elevated for transportation of the load without extending the movable uprights above the fixed uprights. One such solution, which requires an additional cylinder between the uprights to separately elevate the carriage is shown in U.S. Pat. No. 3,394,778 which issued on July 30, 1968, to C. J. Brinton.
The present invention is directed to overcoming one or more of the problems set forth above.
DISCLOSURE OF INVENTION
In one aspect of the present invention, an apparatus has a frame, a first member mounted on and movable relative to said frame, and a second member mounted on and movable relative to said first member. First and second lifting elements are connected to the frame and each have a lifting or extendable portion movable between first and second positions. At the first positions, the second member is movable while the first member is free from being movable. At the second positions, said first and second members are both movable. A load sharing member is connected to the lifting portions of both lifting elements and is movable relative to the first member in response to at least one of the lifting portions moving from its first toward its second position. The load sharing member is movable with the first member in response to at least one of said lifting portions being at its second position.
In another aspect of the present invention, a mast
REFERENCES:
patent: 2456320 (1948-12-01), Repke
patent: 3394778 (1968-07-01), Brinton
patent: 4030568 (1977-06-01), Heinold
patent: 4053139 (1977-10-01), Lovaas
patent: 4191276 (1980-03-01), Farmer et al.
patent: 4219302 (1980-08-01), Leskovec
Heming William B.
Noland Kenneth
Rolla Joseph J.
Towmotor Corporation
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