Material or article handling – Self-loading or unloading vehicles – Conveyor
Reexamination Certificate
2000-03-20
2003-09-23
Walsh, Donald P. (Department: 3653)
Material or article handling
Self-loading or unloading vehicles
Conveyor
C296S181700
Reexamination Certificate
active
06623234
ABSTRACT:
BACKGROUND OF THE INVENTION
The current invention relates to the field of medium duty trailers for hauling highway construction materials. More specifically, the invention relates to an improved trailer of the type employing a continuous conveyor belt system for delivery of material such as asphalt and low-slump concrete in a controlled manner from a new and novel hopper carrying such material to the rear of the hopper and out the rear end of the trailer, such improvements providing better maneuverability, improved material mixing, lower center of gravity, better weight distribution, and increased payload capacity.
The characteristics of trailers with continuous conveyor belt systems for transportation of construction materials are well known to the industry. They have less tendency to overturn than do end dump trailers when the dump bed is elevated. They require less overhead clearance and are less likely to impact low hanging objects, which is also a concern when a dump trailer is in an elevated position. They can deliver large amounts of material at a controlled rate to the job site.
The art in this area is well known. There have been numerous patents pertaining to conveyor belt systems and rear dump trucks in the literature. Some have employed semi-circular shells, such as U.S. Pat. No. 5,482,356 (“Rear Dump Trailer”, Goodson, Jan. 9, 1996). Others, such as U.S. Pat. No. 4,005,790 (“Paving Material Conveyor System”, Holland, Feb. 1, 1977), U.S. Pat. No. 4,664,583 (“Trailer with Conveyor Bed”, Gust, May 12, 1987), and U.S. Pat. No. 5,102,285 (“Trailer with Continuous Conveyer Bed”, Gust, Apr. 7, 1992), describe a flat sided shell with a conveyor belt system mounted underneath. Some describe different types of conveyor belt systems, such as U.S. Pat. No. 4,055,265 (“Bulk Bed”, Eisenman, Oct. 25, 1977), U.S. Pat. No. 4,230,360 (“Bulk Material Bed”, Eisenman, Oct. 28, 1980), and U.S. Pat. No. 4,741,431 (“Conveyor for Bulk Goods”, Whitehead, May 3, 1988). Some types of railroad hopper cars have been observed to have curved sides combined with three bottom discharge chutes along the underside of the car. But to date the combination of independent, discontinuous sides having a cross-sectional aspect of a conic section (or more accurately, with either a circular, elliptical, parabolic, or hyperbolic aspect) with a rear discharge conveyor system has not been considered for such hopper designs
The present invention represents a radical design improvement over previous hopper and continuous conveyor belt designs, and in particular, over U.S. Pat. No. 4,005,790, expired, which was owned by the present assignees.
The linear sided conveyor belt trailer presently in common use exhibits a number of deficiencies and problems. First, the fundamental design of the trailer body requires a number of engineering compromises and trade-offs which, although acceptable at the time the trailer was designed, have resulted in several problems. The manner in which the load is supported during road travel results in frequent maintenance on the rear suspension. The original design of the trailer hopper was one of suspension. Two parallel top beams are longitudinally placed at the upper edges of the trailer walls, and from these beams a set of downwardly extending side braces support the side walls of the trailer. These side braces terminate at a pair of longitudinally extending main beams which are positioned above the conveyor belt system and parallel to the ground. The load is essentially suspended from the top beams which must have sufficient strength to support the sides. This increased weight of the top beams tends to raise the center of gravity of the trailer. Furthermore, since trailer weight is a critical factor in the trailer's use on the highway, the design choice was to evenly distribute the weight of the top and bottom beams between the two units. This results in a bottom beam which, although adequate for the task of carrying the load, is at the lower limits of acceptability; road shock and stress is not completely transferred to the trailer and must be absorbed by the rear suspension. This is one factor which results in a high rate of maintenance for the rear suspension.
Also, the basic flat sided trailer hopper design requires a tradeoff between center of gravity and payload. In order to carry an acceptable payload, the height of the hopper walls must be increased, which results in more of the forward end of the trailer exposed to the wind stream. However, this added weight must be distributed between the rear suspension of the trailer and the rear suspension of the tractor pulling the trailer. A gooseneck configuration is typically the means for transferring weight forward to the tractor, and it tends to keep the forward end of the trailer as low as the back end, resulting in less wind resistance. The conveyor belt system is kept lower than the main beams in order to keep the center of gravity low, but this establishes a minimum distance between the gooseneck and the forward end of the conveyor belt apparatus; if the gooseneck is brought too close to the conveyor belt apparatus, then the rear end of the tractor will interfere with the conveyor belt, especially during turning maneuvers. Thus, there is an inherent limitation on the weight ratio carried by the rear suspension of the trailer and by the rear suspension of the tractor due to this minimum gooseneck-to-conveyor distance. Because of this limitation on weight transfer ratio, more weight can only be carried by either raising the trailer walls or lowering the conveyor belt assembly, and thus the bottom of the trailer bed. These factors represent an inherent limitation in the current design.
Road tracking, or the tendency of the trailer to follow the tractor without deviation, is another factor in current designs. If the center of gravity is too high, then the load will sway unacceptably when changing lanes during highway travel, resulting in increased tendency to tip over. The center of gravity can only be raised until this tendency becomes unacceptable and dangerous, especially in emergency situations. Lower center of gravity improves road tracking.
Second, when the conveyor begins to discharge material from the rear of the trailer, two conditions are observed, namely, that the entire load tends to move out of the rear discharge door as a unit, much like a loaf of bread rather than a stream of material, and the material tends to move longitudinally against the sides of the trailer rather than to fall to the conveyor belt. This longitudinal movement of abrasive material along the inside of the trailer walls results in increased wear of the sides and the necessity for their frequent refurbishment.
Third, because the material tends to adhere to the trailer walls and move in mass when the conveyor is operating, the conveyor belt, sprocket, and chain are exposed to increased stress, since the entire weight of the load is temporarily concentrated on the belt. As the belt continues to move, the load breaks up somewhat, but the tendency is still to resist movement and to press on the conveyor belt. This stress results in increased maintenance to the belt and its mechanical parts, namely, the motor, sprockets, and chain.
Fourth, in order to allow for clearance for various aspects of the conveyor belt system; the extreme rear end of the conveyor belt system must stop before encountering the rear discharge door. This leaves a gap in the bed of the trailer through which material can escape. In order to prevent spillage, a hump or wedge was built into the rear discharge door that would fill the gap between the door and the end of the conveyor belt. While this arrangement prevents spillage, it has the tendency to allow transported material to adhere and cake on the top of the wedge. This is a disadvantage of this configuration of rear discharge door.
Thus, it can be seen that there is a need for a device which has the following characteristics:
1. Lower center of gravity;
2. Less wind resistance;
3. Better road trackability;
4. Higher legal
Griffis David N.
Herring Robert S.
Dan Hill & Associates, Inc.
Harvey III James F.
Rodriguez Joseph
Walsh Donald P.
LandOfFree
Non-linear sided trailer with continuous conveyor bed does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-linear sided trailer with continuous conveyor bed, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-linear sided trailer with continuous conveyor bed will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3032983