Land vehicles: dumping – Tilting – Operating mechanism
Reexamination Certificate
1999-03-11
2001-02-13
Gordon, Stephen T. (Department: 3612)
Land vehicles: dumping
Tilting
Operating mechanism
C298S02200C, C298S02200C, C298S02200C, C298S02200C
Reexamination Certificate
active
06186596
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to new and improved hoists useful for raising or lowering the dump bed of a truck. More particularly, this invention relates to underbody hoists which provide substantially improved lifting efficiency of the hydraulic cylinder and optionally provide a mechanism for locking the cylinder in place to provide greater stability when the dump bed is elevated during the dumping operation.
BACKGROUND OF THE INVENTION
Many types of hydraulic hoists have been developed over the years which are particularly useful as underbody hoists for raising and lowering a dump bed, such as the dump bed of a heavy duty dump truck or trailer. Generally speaking, these hoists employ hydraulic cylinders which, when activated, pivot the dump bed about its rear pivots connected to the frame of the truck chassis.
In a typical hydraulic truck hoist, a hydraulic cylinder lies lengthwise between the framerails of the vehicle and underneath the truck bed. As the hoist's cylinder extends, one end pushes against the underside of the dump bed while the other end of the cylinder, being pivotally attached to the frame members (usually cross members) of the vehicle, pivots to allow the dump bed to raise. At the beginning of the lifting process, the cylinder is nearly parallel to the dump bed and thus has very little initial leverage. Most of the force of the cylinder at this point in the lift process is directed towards the rear hinge that connects the dump bed to the truck frame. Due to this inefficiency, large cylinders are required to provide the substantial forces necessary to achieve this initial lift.
Many types of hydraulic hoists have been developed to address this initial lift problem. In one example, telescopic cylinders are mounted farther forward on the truck frame. This provides the cylinder with greater initial leverage. However, the cylinder in such devices usually must have a rather long stroke to achieve a sufficient dump angle.
Other attempts to improve these hoists have included the use of a simple lever arm to provide the lifting motion in an attempt to obtain a more efficient lift angle. Examples include those hoists disclosed in U.S. Pat. No. 4,052,105. Other designs include those disclosed in U.S. Pat. Nos. 2,509,911; 2,603,518; and 4,762,370. These patents disclose hoist designs where a lever provides the initial lift of the truck bed, and a cylinder completes the lifting process.
Generally speaking, truck hoist designs known prior to the subject invention have one or more drawbacks associated with their use. For the most part, they often require large and expensive cylinders. Many are difficult to install or manufacture. Other designs are subject to large stresses, are potentially unstable when elevated, or do not achieve superior initial lift. Stability problems have been known to occur, for example, when wet loads are carried and the entire load is not eliminated during the dumping operation, leaving, for example, some of the load in the most elevated part of the dump bed.
In view of the above, it is apparent that there exists a need in the art for a hoist which can efficiently raise and lower a truck bed and which is not subject to the above drawbacks. It is a purpose of this invention to fulfill this need in the art, as well as other needs which will become apparent to the skilled artisan once given the following disclosure.
SUMMARY OF INVENTION
Generally speaking, this invention fulfills the above-described needs in the art by providing a hoist for raising or lowering a truck bed to and from a truck frame which is capable of being located between the bed and the frame, the hoist comprising: an extendible and retractable cylinder connected at one end to a lever mechanism and at the other end connectable to the underside of a bed, the lever mechanism comprising at least a first pivot, a first pivot centerline, a second pivot, and an elongated arm, the first pivot being attachable to a truck frame and the second pivot being rotatably attached to the cylinder, the second pivot being located at a first offset distance from the centerline of the first pivot, and being rotatable about the first pivot when the cylinder is extended or retracted, the elongated arm being pivotally connected to the first pivot at one end and comprising a first roller mechanism for engagement with a truck bed at the other end, the elongated arm extending and angling upwardly from the first pivot; the lever mechanism being so located that when the cylinder is caused to extend, the cylinder pushes against the lever mechanism causing the lever mechanism to rotate about the first pivot, and causing the elongated arm to raise the bed from the frame; the hoist further including a stop mechanism so located at a selected offset distance from the first pivot centerline opposite the side of the first pivot centerline of the first offset distance, such that when the second pivot is caused to rotate into contact with the stop mechanism, further extension of the cylinder causes the cylinder to raise the bed further from the frame.
In certain further embodiments of this invention, a hoist for raising or lowering a truck bed to and from a truck frame capable of being located between the bed and the frame comprises: an extendible and retractable cylinder connected at one end to a lever mechanism and at the other end connectable to the underside of the bed, the lever mechanism comprising at least a first pivot, a second pivot, and an elongated arm, the first pivot being attachable to the truck frame and the second pivot being rotatably attached to the cylinder, the second pivot being located at a first offset distance from the centerline of the first pivot, and being rotatable about the first pivot when the cylinder is extended or retracted, the elongated arm being pivotally connected to the first pivot at one end and designed for engagement with the truck bed at the other end, the elongated arm extending from the first pivot; the lever mechanism being so located that when the cylinder is caused to extend, the cylinder pushes against the lever mechanism causing the lever mechanism to rotate about the first pivot, and causing the elongated arm to raise the bed from the frame; the hoist further including a stop mechanism such that when the lever mechanism is caused to stop by the stop mechanism, further extension of the cylinder causes the cylinder to raise the bed further from the frame; the hoist further comprising a locking device to lock the second pivot at its point of rotation about the first pivot.
In certain other embodiments, the locking device comprises at least one locking mechanism pivotally connected to the hoist, at least one linkage mechanism pivotally attached to the lever mechanism on the first pivot and pivotally attached to the locking mechanism, a second roller mechanism pivotally attached to the linkage, whereby, when the cylinder raises the bed, the second roller mechanism rolls against the cylinder causing the linkage mechanism to position the locking mechanism against the force of a biasing mechanism, such that the second pivot locks at its position of rotation about the first pivot.
In still further embodiments, a track mechanism is provided which is connectable to the underside of the truck bed for engagement with the elongated arm. This track may extend either parallel to or at angle to the truck bed.
This invention will now be described with respect to certain embodiments thereof as set forth in the accompanying illustrations, wherein:
REFERENCES:
patent: 2509911 (1950-05-01), Dore
patent: 2603518 (1952-07-01), Golay
patent: 3211428 (1965-10-01), Spracklin
patent: 3594042 (1971-07-01), Gauch
patent: 4029358 (1977-06-01), Bergdolt
patent: 4052105 (1977-10-01), Moe
patent: 4176881 (1979-12-01), Cole
patent: 4762370 (1988-08-01), Corompt et al.
patent: 5048896 (1991-09-01), Channell
Gordon Stephen T.
Hall Priddy Myers & Vande Sande
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