Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1982-06-25
1985-07-30
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
414631, B66B 920
Patent
active
045316155
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to a mast assembly for lift trucks and more particularly to a lift system for selectively raising and lowering a movable upright on a fixed upright of the mast assembly.
BACKGROUND ART
One type of conventional lift truck employs a lift system including a cylinder and a pair of chains mounted centrally of a mast assembly thereof. Such disposition of the cylinder and chains tends to impair the forward visibility of the truck's operator. Various solutions have been proposed to solve this problem, such as by positioning a lift chain directly behind the cylinder and/or by displacing the cylinder laterally and adjacent to an upright channel of the fixed upright of the mast assembly.
Prior art solutions of the latter type have not fully solved the visibility problem and in many designs tend to increase the overall complexity and number of component parts employed in the mast assembly. In addition, such designs give rise to load balancing and sequencing problems and do not afford the desired protection to operating components thereof.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF INVENTION
In one aspect of this invention, a lift truck mast assembly comprises a fixed upright assembly having laterally-spaced uprights adapted for mounting on a lift truck, a moveable upright assembly mounted on the fixed upright assembly, at least one chain secured at opposite end portions to the fixed upright assembly, a pair of laterally spaced chain guides mounted on a lower end portion of the moveable upright assembly and having the chain entrained thereunder to form a pair of vertically disposed and laterally-spaced chain portions, and actuating means engaging the chain between one end of the chain and the chain guides for selectively raising the moveable upright assembly on the fixed upright assembly in response to extension of the actuating means and for lowering the moveable upright assembly on the fixed upright assembly in response to retraction of the actuating means.
In another aspect of this invention, a lift truck has a mast assembly mounted forwardly theron which comprises a fixed upright assembly having laterally-spaced first and second uprights, a moveable upright assembly slideably mounted on the uprights, a pair of laterally-spaced sheaves mounted on a lower end portion of the moveable upright assembly, a fluid cylinder having a lower end portion attached to the fixed upright assembly and an upper end portion attached to a sheave, and a chain having a first end portion attached to the first upright and a second end portion attached at least closely adjacent to the second upright. The chain is sequentially entrained from its first end portion over the sheave attached on the cylinder and under the sheaves mounted on the moveable upright assembly to raise the moveable upright assembly on the fixed upright assembly in response to extension of the fluid cylinder and to lower the moveable upright assembly in response to retraction of the fluid cylinder.
The improved mast assembly of this invention will provide the operator of a lift truck or other type of industrial vehicle with a high degree of forward visibility through the mast assembly. In addition, the lift system for the mast assembly is composed of a minimum number of well-protected component parts, including the highly reliable single stage single-acting hydraulic cylinder with flow control. The lift system also avoids load balancing and sequencing problems normally encountered with conventional dual cylinder or offset cylinder designs.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of this invention will become apparent from the following description and accompanying drawings wherein:
FIG. 1 illustrates a lift truck employing a mast assembly embodiment of the present invention thereon, with the mast assembly shown in its extended condition of operation;
FIG. 2 is a rear elevational view of the mast assembly;
FIG. 3 is a side el
REFERENCES:
patent: 2139597 (1938-12-01), Martin
patent: 2670811 (1954-03-01), Shaffer
patent: 3187842 (1965-06-01), Quayle
patent: 3208556 (1965-09-01), Shaffer
patent: 3851732 (1974-12-01), Wagner et al.
patent: 3985207 (1976-10-01), Petit
patent: 4356891 (1982-11-01), Bartow
patent: 4392554 (1983-07-01), Russey
Noland Kenneth
Rolla Joseph J.
Towmotor Corporation
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