Implements or apparatus for applying pushing or pulling force – Hoisting truck – Single throw lever
Reexamination Certificate
2000-05-01
2001-08-21
Banks, Derris H. (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Hoisting truck
Single throw lever
C254S124000
Reexamination Certificate
active
06276665
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to floor cranes and more particularly to mobile floor cranes used in the automotive aftermarket.
Conventional mobile floor cranes such as shown in U.S. Pat. Nos. 3,931,956 and 4,669,703 typically have a pair of legs and a cross piece forming a bridge connecting the two legs and supporting the central upright stanchion of the crane. The legs and the cross piece typically are formed of tubular steel for increased strength. However, the strength of the cross piece and the strength of its connection to the two legs limit the amount of weight that can be lifted by the crane. The lateral distance between the stanchion and the legs provides a bending moment that can apply a twisting force to the legs and cause the crane to fail. Attempts to stabilize the legs against twisting have included the provision of a caster under each leg in the vicinity of the crosspiece as shown in U.S. Pat. No. 5,076,448. However, this then shifts the load from being carried by the rear wheels to being carried by the wheels beneath the legs by the crosspiece, and this shift has the undesirable effect of reducing the overall footprint of the load-carrying components of the crane. In the end, one type of instability is traded for another type of instability.
Moreover, construction of these so-called bridge-type cranes wherein the cross piece forms a bridge between the two legs, involves multiple manufacturing operations like metal cutting, hole-drilling, positioning, welding, and bolting. These manufacturing operations, and particularly the welding operations, add significantly to the overall cost of the crane. For example, the cross piece must be sized and cut, and in some embodiments the cross piece must be welded to the base and/or the legs. A crane design that could eliminate the cross piece might be produced less expensively than a comparable bridge-type crane due to the elimination of fabrication materials, fabrication time, and fabrication operations involving the cross piece.
Precise positioning of the parts relative to one another before they are welded also plays a significant role in the cost of manufacture of these conventional cranes. If the upright stanchion is located off-center relative to the two legs, then the load carried by the stanchion will not be evenly distributed between both legs of the crane. The off-center stanchion may wiggle or tend to tilt in use. Thus, siting of the stanchion atop the cross piece must be done with care, or the stanchion will be off center and the crane will need to be rejected. Rejects lead to waste that increases the cost of production. Moreover, the cumulative tolerances for the parts involved in positioning the stanchion can result in errors that cause a misalignment that might not be detectable by the eye of the user who assembles the crane.
OBJECTS AND SUMMARY OF THE INVENTION
It is a principal object of the present invention to provide an improved mobile floor crane that has an equivalent or greater lifting capacity as conventional cranes yet is configured so as to be less costly to manufacture.
It is another principal object of the present invention to provide a method of making a mobile floor crane that reduces the cost of making the crane without sacrificing the lifting capacity of the resulting crane.
It is a further principal object of the present invention to provide a mobile floor crane that easily disassembles for shipment and storage yet is less expensive to manufacture than a conventional crane without any reduction in the lifting capacity of comparable conventional cranes.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
A portable lifting device such as a mobile floor crane includes a stanchion carried by a mobile base. The base can be rendered mobile by wheels, rollers, or casters attached to the base. The wheels, rollers, or casters are disposed symmetrically with respect to a stanchion carried by the base. The base is formed by a pair of legs that are configured identically and disposed so as to be mirror images of each other. The stanchion is a rigid, vertically elongated, upright member that is centrally disposed relative to the legs. The stanchion is desirably formed of tubular steel having a generally rectangular transverse cross section along the entire length thereof.
Each leg is desirably formed of tubular steel having a generally rectangular transverse cross section along the entire length thereof. Each leg has a rear portion, a mid portion, and a forward portion. In forming the base, the legs are disposed alongside one another such that the mid portions are side-by-side and opposed to one another such that each leg is the mirror image of the other. Along the mid portions of the legs, the legs are separated from each other by a distance that is not substantially more than the width of the stanchion. Each leg has a means for rendering the crane mobile. This typically can include a wheel assembly to support the free end of the forward portion of each leg and a caster to support the free end of the rear portion of each leg.
In accordance with a presently preferred embodiment of the invention, the base end of the stanchion is disposed between the mid portions of the legs and mounted on a support bolt passing transversely through the mid portions of both legs and the base end of the stanchion. In the preferred case, the separation between the mid portions of the legs only allows sufficient clearance for the stanchion to be pivotable about the support bolt during assembly. Once assembled, the support bolt desirably places the stanchion and the mid portions of the legs under compression, thus substantially reducing any bending moments that might twist the legs under load.
In still further accordance with a presently preferred embodiment of the invention, the mid portions of both the left and right legs are permanently attached to a unitary tubular member that functions as the rear portions of both legs and defines the spacing between the mid portions of the legs. In an alternative embodiment, a spacer is disposed between the mid portions of the legs in the vicinity of the rear portions of the legs. The spacer is formed by a rigid block that has substantially the same width as the width of the stanchion. The unitary tubular member and the spacer desirably can be formed of the same stock of tubular steel as the stanchion. In another alternative embodiment, a back brace is disposed between and connecting the rear portions of the legs.
In accordance with a presently preferred embodiment of the invention, an obtuse angle is formed between the mid portion and the forward portion of each leg. Desirably, this angle is formed by bending the unitary tubular member that is used to form each leg.
In accordance with a presently preferred embodiment of the invention, a second angle is formed between the rear portion and the mid portion of each leg. In an alternative embodiment, this angle is also formed by bending the unitary tubular member that is used to form each leg.
By eliminating the cross piece and supporting the stanchion on the support bolt, the bending moment associated with the cross piece is also eliminated. Thus, the crane of the present invention is stronger than conventional cranes of the same dimensions and thus has greater lifting capacity. Moreover, the lifting device of the present invention is less costly to manufacture than conventional cranes. Because of the construction of the lifting device of the present invention, it is less likely that the stanchion will be installed off center.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and, together with the d
Blackburn John H.
Brookshire Roy David
Hawkins Joseph O.
Hawkins Terry Jerome
Stewart Frances Hawkins
Banks Derris H.
Dority & Manning P.A.
Shanley Daniel
Sunex International Inc.
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