Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
2000-08-03
2002-05-28
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S778000
Reexamination Certificate
active
06394261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present application relates to variable counterweighted take-up assembly for endless conveyors and endless conveyor system incorporating such take-up assembly. The invention also relates to endless conveyors incorporating such variable counterweighted take-up assembly. Although all types of endless conveyors are included, conveyors having a helical belt path are particularly contemplated.
2. Description of the Related Art
Endless conveyors of the type contemplated herein generally include an endless conveyor belt which has sufficient flexibility to allow the belt to traverse an endless path from a product input station to a product discharge station, and thereafter to return from one station to the other via a return section. When the conveyor path is straight, the belt must be capable of flexing along an axis generally perpendicular to the path. When the path is other than straight, such as a helical path of the type contemplated herein, the belt must be capable of flexing at least to a limited extent along at least three mutually orthogonal axes in order to permit the belt to traverse such relatively complex paths.
In order to permit such multi-directional flexing, such conveyor belts are generally constructed of a plurality of interconnected links which permit at least limited link-to-link articulation along two or more mutually orthogonal axes. In such instances, the links are generally constructed of a material such as steel making the weight of the belt a relatively significant factor in operating the conveyor system.
Conveyor belts of the type contemplated herein generally range from about 12 inches to about 60 inches in width and from about 200 feet to about 2,500 feet in length, and even up to about 3,000 feet in some instances. When a conveyor belt is constructed of numerous interlocked steel links and is between 10 and 60 inches in width and more than 200 feet in length, the weight of the belt becomes a significant factor to reconcile. For example, the belt must be driven through the work path which begins at the product input station and ends at the product discharge station. Thereafter, the belt enters the return section where it reverses direction and re-enters the product input station to continue operating in its endless path. In helical conveyors, the belt is driven up a helical shaped path in an up-go conveyor, and down a helical shaped path in a down-go conveyor. The belt is generally driven by friction forces imparted to it along the inner edge by a circular shaped rotating cage around which the belt is wrapped in the work zone, and it is provided with additional assistance by a motor driven sprocket which is constructed to engage the links of the belt directly as it is rotatably driven by the assist motor. Such motor assist is particularly needed in up-go helical conveyors where the relatively heavily weighted belt is made to traverse an up-go helical path against the force of gravity. A motor driven assist sprocket is also utilized in helical shaped down-go conveyors, although the gearing and roller arrangements differ somewhat from the up-go conveyors, and the assist force required is somewhat different. In other applications, the work zone of the conveyor path is straight.
Conveyor belts of the type contemplated herein are generally used for conveying products under various conditions. For example, in some applications, the belts are used to convey dough products through relatively high temperature atmospheres in order to assist the dough in rising prior to formation of a bread product. In other applications, the belts may be made to carry food products through relatively cold atmospheres, sometimes under freezing conditions. In still other applications, the belts may be required to conduct products at room temperature.
In each instance, the belt, being made of a plurality of interlocked metal links, will react to the surrounding conditions such as temperature, cleanliness and the like, with the result that the belt will undergo a natural stretch or compression such factors will, in turn, affect the belt tension. In some instances, the belt will become longer during operation and, in others, the belt may become shorter, and such variations in these vital parameters have necessitated the incorporation of a take-up section in the belt return section of the system in order to permit the accumulation of excess belt and to accommodate the increases and decreases in the length of the belt. Further, since the belt is constructed of numerous interconnected links, variations in the link-to-link spacing at any given time will also accumulate to change the overall length of the belt.
In helical conveyors, the belt will undergo compression along the inner edge of an arcuate turn and stretch along the outer edge, thus resulting in relatively complex changes in the overall conditions such as tension and length of the belt. These changes have also been found to affect the overall tension in the belt throughout the system, with the result that in some instances, particularly where sanitary conditions are not observed, the belt tension will differ between separate locations along the path.
It has been found that ideally, belt tension should be maintained as uniform as possible, and this objective has often been met with some success in the past by incorporating a take-up section in which excess belt is permitted to accumulate. In the take-up section, the excess belt is made to pass through two adjacent sections, a first fixed section and a second variable section. In the first fixed section, a portion of belt is maintained in the form of a vertical curtain of fixed length and weight. In the second variable section, the excess belt is looped under and about a floating dancer roller so as to assume a generally V-shaped configuration, and is permitted to increase and decrease in dependence upon increases or decreases in the length of the belt as may be caused by operating conditions. The weight of the portion of belt in the second variable section belt is maintained in counterbalance relation to the weight of the curtain of belt in the first fixed section such that when the length and weight of the belt in the second fixed section increases, the dancer arm moves to its lowermost position, and when the length and weight of the belt in the second variable section decrease, the dancer arm moves upwardly toward its uppermost portion.
In order to maintain a proper balance between the portions of belt in the first fixed and second variable sections, prior art systems have attached a fixed weight to the dancer arm in the second variable section. The weight is intended to complement the weight of the belt portion therein and to counterbalance the weight of the vertical curtain of belt in the first fixed section. It can be readily appreciated that a balanced or unbalanced condition between the two sections will in turn affect the tension on the belt in the entire endless system. Accordingly, the need to maintain a proper balance between the first and second systems is readily obvious. Ideally, it is preferable to maintain the weight of the belt portion in the second variable section at a constant level, or at least to within a predetermined relatively narrow range substantially equal to the weight of the belt portion in the first fixed section.
U.S. Pat. No. 4,189,047 to Beckius relates to an endless conveyor wherein the tension of the belt carrying the product cannot be readily adjusted during operation. A progressive counterweight is provided for tensioning the belt where lengthening of the portion of the belt carrying the product automatically reduces the tension force and shortening the belt carrying the product automatically increases the tension force. The amount of weight varies depending upon the vertical positioning of weights and supports within a column
70
. German Patent No. 263,275 relates to a conveyor belt tensioner which acts during extreme conditions. Tensioning drum
1
is connected by a tensioning cable
Bidwell James R.
Hoffmann & Baron , LLP
Tarpaulin.Com, Inc.
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