Conveyors: power-driven – Conveyor section – Spiral
Reexamination Certificate
2000-11-15
2003-02-25
Ellis, Christopher P. (Department: 3651)
Conveyors: power-driven
Conveyor section
Spiral
C198S781040
Reexamination Certificate
active
06523677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a low tension dual helical conveyor systems capable of conveying articles along concentric helical paths having mutually opposite directions of travel.
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 travel over concentric helically shaped paths having opposite directions of travel from a product input station to a product discharge station. Since the path is helical, 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 follow such a relatively complex path. With concentric helical paths, the flexibility of the belt along several axes is increasingly significant, particularly when the helical paths are connected by a cross-over section of conveyor belt.
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 materials such as steel, plastics, combinations thereof or the like, 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 above about 200 feet in length. Although single helical conveyors generally may be of length up to about 5,000 feet, the possible length of such conveyors is virtually unlimited. When a conveyor belt is constructed of numerous interlocked steel links and is between 12 and 60 inches in width and more than 200 feet in length, the substantial 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.
In certain systems, such as the dual concentric conveyor systems disclosed in U.S. Pat. Nos. 3,664,487 and 4,036,352, the belt is driven by positive drive forces provided by drive members such as rotating drive angles driven on one side of the helical loops. In other systems in which a single helical path is defined, the belt is driven by friction forces imparted to it along the inner edge by a circular shaped rotating cage having friction/slip members attached to it and around which the belt is wrapped in the work zone. When the belt is friction driven, it generally is also provided with additional assistance by a motor driven sprocket which is constructed and arranged 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 general, positively driven belts are subjected to greater tensile forces then the belts which are driven by friction forces due in part to the fact that the friction drive surface is generally moving at a faster rate of speed than the rate of speed of the driven edge of the belt. For example, when a friction driven belt of about 36 inches in width travels one revolution, the friction drive mechanism will travel approximately 36 inches further than the corresponding driven edge of the belt.
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 temperatures, 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. For example, some instances, the belt will become longer during operation and, in others, the belt may become shorter. Such variations sometimes make it relatively difficult to drive the belt by friction drive devices, since positively driven systems are relatively less complicated to control.
Dual concentric helical conveyor systems of the type disclosed in U.S. Pat. Nos. 3,664,487 and 4,036,352, which are positively driven, generally utilize conveyor belts which are permanently curved to meet the curvature of the helical conveyor paths and to accommodate the positive drive systems. In such instances, the permanent curvature in the belt also accommodates the transitional portion—or cross-over section—which connects both main conveyor systems. Further, the permanent curvature accommodates the positive drive mechanism by providing relative synchronized precision between the positive drive mechanism and the belt in both of the main conveyor sections.
Positively driven dual concentric helical conveyor systems have a number of disadvantages. For example, the preset curvature in the belt limits the location and angle of the “product infeed/product discharge” sections. Also, the preset curved nature of the belt prevents reversing the belt to reduce wear and increase belt life. Moreover, the significant tension to which the belt is normally subjected by the positive drive mechanism tends to increase belt wear and limit belt life. We have invented a dual concentric conveyor belt system which incorporates low tension friction drive systems in both of the main conveyor sections which permits the use of a normally straight flexible conveyor belt. In addition, we have invented a low tension friction drive system which can be incorporated into the cross-over section of the main conveyor sections in a manner to communicate the main conveyor sections with a low tension friction drive system, independent of whether the main sections are driven by friction or by positive drive devices, all while reducing the wear on the conveyor belt.
SUMMARY OF THE INVENTION
The invention relates to a dual helical conveyor system, which comprises a conveyor belt adapted to move in a first direction along a first helical path and thereafter in a second direction generally opposite the first direction along a second helical path inside the first helical path. Preferably the first and second helical paths are generally concentric. The conveyor belt is further movable through a cross-over section along a cross-over path connecting the first and second helical paths. A conveyor belt drive mechanism is provided in the cross-over section to frictionally drive the conveyor belt along the cross-over path and between the first and second helical paths. The conveyor belt is driven by a first friction drive mechanism along the first helical path, and a second friction drive mechanism along the second helical path. The conveyor belt defines a product input/discharge section at at least two locations, and a conveyor belt return device is provided to guide the conveyor belt between the first and second helical paths. The conveyor belt return device comprises a generally circular shaped guide
DeGennaro Ronald J.
Finazzo, Jr. Jerome J.
Priebe Paul
Wedell Thomas
Crawford Gene O.
Ellis Christopher P.
Tarpaulin.COM, Inc.
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