Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1980-08-22
1983-01-04
Tollberg, Stanley H.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
414631, 308 3CH, B66B 920
Patent
active
043668836
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
The present invention relates to a load lifting apparatus having two laterally spaced apart motors, and particularly to a load equalizing system which maintains substantially equal tension in a pair of laterally spaced apart chain assemblies during load lifting operations.
BACKGROUND ART
Lift trucks having two laterally spaced apart motors, or fluid cylinders, each of which has associated therewith a respective chain assembly, provide excellent forward visability through the space between the cylinders. However, due to the wide stance of the chain assemblies, vertical rotations of a load support, such as when an off-center load is upon the load support, result in uneven tensions in the chain assemblies. These unequal tensions reduce the life of the chain assemblies, place unnecessary and unequal loading on the cylinders, and tend to over-stress other lifting components.
Devices are known to the art for single cylinder lift trucks which equalize the load between a pair of chain assemblies associated with the single cylinder. For example, U.S. Pat. No. 4,010,825, issued Mar. 8, 1977, inventor Charles R. Chelin, discloses a pivot element which is interconnected between a pair of chain assemblies and connects the chain assemblies to a carriage which carries a load. The pivot element causes equalization of the load between the chain assemblies in single engine lift trucks in response to an excessive load being imposed on one of the chain assemblies.
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 this invention, a load equalizing system is provided with a load lifting apparatus. The load lifting apparatus has a support structure, a movable structure, a load support, first and second chain assemblies and first and second linearly movable motors. The load equalizing system moves one of said motors a predetermined distance relative to the other of said motors and to said movable structure to maintain substantially equal tension in said chain assemblies.
Accordingly, unequal stresses upon the chain assemblies are substantially reduced, and the useful lives of the chain assemblies are extended.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial side elevational view of a vehicle incorporating an embodiment of the present invention;
FIG. 2 is a front elevational view partially broken away and with details in section, of a vehicle as in FIG. 1;
FIG. 3 is a front elevational view similar to FIG. 2, but illustrating a different relative position of components therein;
FIG. 4 is an enlarged perspective view of an embodiment detail in accordance with the present invention;
FIG. 5 is a view similar to that of FIG. 4, but of another embodiment; and,
FIG. 6 is a front elevational view, partially in section, of the embodiment as in FIG. 5.
BEST MODE OF CARRYING OUT THE INVENTION
Referring to FIG. 1, a mast assembly 10 of a load lifting apparatus, or lift truck, 12 includes a generally vertically movable carriage, or load support, 14 connected thereto and adapted to support a load 16. Referring to FIG. 2, a relatively stationary support structure 26 has a pair of laterally spaced apart, relatively stationary outer mast members 28 with upper ends 29. A movable structure 42 is mounted on support structure 26 and can be vertically moved with respect to lift truck 12. Movable structure 42 includes a pair of laterally spaced apart, inner uprights 44. Uprights 44 are interconnected at upper ends 46 thereof by a longitudinally extending tie bar 48. Tie bar 48 has distal portions 50 which transversely extend beyond uprights 44. When tie bar 48 is in a lowermost position it will rest upon upper ends 29 of outer mast members 28.
A clevis 52 is affixed to one distal portion 50 and has a downwardly depending, inboard side 53 and a downwardly depending, outboard side 54. An equivalent clevis 52 is affixed to the other distal portion 50.
A first lift cylinder, or motor, 56, and a second lift cylinder, o
REFERENCES:
patent: 2415014 (1947-01-01), Luebbers
patent: 2787338 (1957-04-01), Quayle
patent: 3202242 (1965-08-01), Dolphin
patent: 3834668 (1974-09-01), Casey
patent: 4010825 (1977-03-01), Chelin
patent: 4170340 (1979-10-01), Mouton, Jr.
Hickman Alan J.
Noland Kenneth
Tollberg Stanley H.
Towmotor Corporation
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