Roller suspension

Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support

Patent

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Details

187 95, 308 3B, 308184R, B66B 920

Patent

active

043752470

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION



Technical Field

The present invention is related to a roller mounting structure and in particular to a roller mounting structure for the carriage and mast of a lift truck.


Background Art

Carriage mounting arrangements and lift mast mounting arrangements of the type shown in U.S. Pat. No. 3,851,732, issued to R. A. Wagner, et al on Dec. 3, 1974, are well known. In general, the lift mast mounting includes a movable upright which is longitudinally movable within a fixed upright by disposing a plurality of rigidly mounted wheels or guide rollers therebetween. The carriage mounting arrangement includes a carriage which is longitudinally moved with respect to the movable upright by disposing another plurality of rigidly mounted wheels or guide rollers therebetween.
It has been observed that the roller engaging surface of the uprights experiences wear and surface flaking after extended periods of operation due to misalignment of the roller with the upright. This misalignment is caused, in part, by uneven loading of the carriage forks and the unevenness of the rollers and uprights as manufactured. The wear and flaking is the result of a relatively small area of total contact between the edge of the hardened steel tread portion of the rollers and the surface upon which they roll, which produces high contact stresses. Even higher levels of contact stresses are generated with the increased distortion of the surface caused by continuing flaking and with further misalignment of the rigidly mounted rollers. In order to minimize these stresses, close control of the material utilized along with close control of the manufacturing and assembly of the rollers and uprights has been found necessary. However, despite all these precautions, excessive wear of the roller engaging surface is still experienced.
A solution to this problem can be found in U.S. Pat. No. 4,035,040, issued to William T. Yarris on July 12, 1977, and relating to a self-alignment wheel mount structure. This device calls for a supporting axle shaft having a crown bearing seat thereon and a bearing assembly which mounts on the seat. The bearing assembly includes an inner race having a substantially cylindrical internal bore rockably mounted on the crowned bearing seat. This wheel mounting structure is self-alignable and reacts to imperfections in the load bearing surface of the uprights to assure optimum contact between the roller and the surface upon which it rolls. However, such a system requires accurate machining and, thus, is expensive to manufacture. Further, such a system does not provide for load sharing between the various rollers which secure the carriage to the movable upright and the movable upright to the fixed upright.
Another prior art device which addresses this problem includes an elastomeric ring member positioned between the shaft and the bearing assembly and provides self-aligning of the roller with respect to the surface upon which it rolls. Such an arrangement can provide for limited absorption of shock due to impact loading of the carriage.
Another approach used to solve the above problem is to crown the outer diameter of the roller to reduce the edge-loading tendency. However, this reduces the roller contact or footprint with the surface of the upright and therefore increases the contact stress. Further, such an arrangement also requires expensive machining.
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 mounting structure has an axle shaft and a bearing assembly positioned about the axle shaft and the improvement comprises a spring being positioned between the bearing assembly and the axle shaft.
The above invention provides an inexpensive and efficient way to have a roller which is self-aligning and thus, responsive to any forces placed thereon; as, for example, by the uneven loading of the carriage of the lift truck. When uneven loading does occur, the spring is deflected allowing the roller to have f

REFERENCES:
patent: T981004 (1979-04-01), McNeely et al.
patent: 1152680 (1915-09-01), Wieselgreen
patent: 2092291 (1937-09-01), Olsen
patent: 2238435 (1941-04-01), Perry
patent: 3070190 (1962-12-01), Rogers et al.
patent: 3083853 (1963-04-01), Hastings, Jr.
patent: 3447846 (1965-08-01), Marsh
patent: 3604545 (1971-09-01), Bourgeois
patent: 3690639 (1972-09-01), Brandon et al.
patent: 3871494 (1975-03-01), Kelley, Jr.
patent: 3976340 (1976-08-01), Pitner
patent: 4035040 (1977-07-01), Yarris
patent: 4240526 (1980-12-01), Sanders

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