Miscellaneous hardware (e.g. – bushing – carpet fastener – caster – Casters – Adjustable
Reexamination Certificate
2000-06-13
2001-08-28
Mah, Chuck Y. (Department: 3626)
Miscellaneous hardware (e.g., bushing, carpet fastener, caster,
Casters
Adjustable
C016S044000, C016S034000
Reexamination Certificate
active
06279199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to spring biased caster wheels capable of vertical adjustment wherein a uniform biasing force is maintained on the caster wheel regardless of its vertical adjustment.
2. Description of the Related Art
Caster wheels capable of vertical adjustment with respect to the supporting frame are known, but if the caster wheel is to be spring biased or suspended, difficulty is encountered in producing a uniform biasing force on the caster wheel regardless of its vertical position.
In hand operated fork lifts, for instance, spring biased heavy duty caster wheels are employed. It is desirable to permit such caster wheels to be vertically positionable for a number of reasons, including wheel wear and floor clearance, but it is important that the spring biasing force on the caster wheel be uniform regardless of the caster wheel vertical position. In known spring biased caster wheel constructions, difficulty has been encountered in maintaining a uniform biasing force on the caster wheel as the vertical position of the wheel is adjusted.
Because of the concise configuration of caster wheels, it is difficult to incorporate spring biasing means within the caster wheel which will provide a uniform biasing force regardless of the wheel vertical position. With such types of casters, uniformity and control of biasing forces is usually sacrificed if vertical adjustment is desired.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a heavy duty spring biased caster wheel capable of vertical adjustment upon its supporting frame.
Another object of the invention is to provide a heavy duty spring biased caster wheel vertically adjustable upon its frame wherein the spring biasing force characteristics are uniform regardless of the vertical position of the caster wheel upon its frame.
Yet a further object of the invention is to provide a heavy duty vertically adjustable spring biased caster wheel having uniform biasing characteristics regardless of its vertical position and wherein forces imposed upon caster structure are balanced and equalized.
SUMMARY OF THE INVENTION
A heavy duty caster wheel in accord with the invention is mounted upon a frame having an upper region attached to the structure being supported by the caster, and such mounting structure often includes rotatable bearings permitting the frame to be rotated about a vertical axis so that the caster wheel may orient itself to the direction of movement of the structure which it is supporting.
The lower region of the caster frame consists of a pair of parallel spaced side plates. A primary pivot shaft extends through vertically defined slots in the frame side plates and the pivot shaft extends through the side plate slots into supporting blocks adjustably mounted upon the outer side of the frame side plates. In this manner, the pivot shaft is vertically positionable with respect to the frame.
A caster wheel support of a U-configuration is located between the frame side plates and is pivotally mounted upon the pivot shaft. A caster wheel is rotatably mounted upon the caster wheel support upon an axle radially spaced from the pivot shaft and vertical pivotal movement of the caster wheel results from pivoting of the caster wheel support on the pivot shaft.
A spring cradle is located between the frame side plates and is also pivotally mounted upon the pivot shaft for vertical adjustment therewith. The spring cradle includes torque restraint means which restrain the spring cradle against pivotal movement on the pivot shaft, and compression springs interposed between the spring cradle and the caster wheel support produce a biasing force on the caster wheel support tending to pivot the caster wheel support, and caster wheel, in a direction for engaging the caster wheel with the floor or caster wheel supporting surface.
The spring cradle is restrained against pivoting on the pivot shaft by a bar affixed to the spring cradle radially spaced from the pivot shaft. The ends of the bar constitute studs which are slidably received within vertically oriented grooves or slots defined in the frame side plates. Accordingly, the slidable movement of the studs within the grooves permits the pivot shaft and spring cradle to be vertically positioned as desired, but the grooves prevent the spring cradle from pivoting upon the pivot shaft due to the biasing forces of the compression springs. Accordingly, as the location of the ends of the compression springs relative to the spring cradle and the caster wheel support do not change even though the pivot shaft is vertically adjusted on the frame side plates, the biasing force on the caster wheel will remain uniform regardless of the caster wheel's vertical adjustment.
The blocks receiving the ends of the pivot shaft include vertical slots receiving bolts whereby the blocks may be vertically adjusted upon the adjacent frame side plate outer surface. To enhance the frictional engagement between the pivot shaft supporting blocks and the side plates, a plurality of serrations forming grooves and tongues are formed on the side plate outer side and the inner side of the blocks wherein tightening of the screws will intermesh the tongue and grooves to produce a high strength adjusted position of the pivot shaft. Of course, other types of supports and threaded adjustments can be used to support the ends of the pivot shaft relative to the frame side plates.
The wheel support and spring cradle are all located within the confines of the frame side plates, and a caster construction in accord with the invention is capable of withstanding a high degree of abuse without significant damage, and the vertical adjustment of the pivot shaft permits the caster wheel to be accurately vertically adjusted relative to the caster frame, and yet the predetermined spring characteristics of the caster wheel will be maintained regardless of the vertical adjustment of the caster wheel.
REFERENCES:
patent: 2894761 (1959-07-01), Knarzer
patent: 4372569 (1983-02-01), Otterson
patent: 4685174 (1987-08-01), Hager
patent: 4763910 (1988-08-01), Brandli et al.
patent: 5347680 (1994-09-01), Rippe
patent: 5400469 (1995-03-01), Simonsen
patent: 5581843 (1996-12-01), Purnell
patent: 59-48202-A (1984-03-01), None
patent: WO-94/16599-A1 (1994-08-01), None
Mah Chuck Y.
Ross Design & Engineering, Inc.
Young & Basile P.C.
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