Conveyor device

Conveyors: power-driven – Conveyor section – Endless conveyor

Reexamination Certificate

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Details

C198S806000

Reexamination Certificate

active

06286663

ABSTRACT:

The invention relates to a conveyor device, having a conveyor belt that revolves around at least two rollers, in which at least one of the rollers is held rotatably on a rotary bearing and is displaceable at least partly in the axial direction relative to the rotary bearing.
Belt conveyor systems used as continuous conveyors are employed today not only for conveying purposes but increasingly also in conjunction with a further treatment of the product being conveyed. Particularly in the food industry, drying of foods conveyed on the conveyor belt has gained an importance. For the drying, a heating element disposed between the upper and lower runs of the conveyor belt is used. For promoting the drying process, the conveyor belt can also be disposed in an evacuatable vacuum chamber. To assure high efficiency of the drying system, typically especially thin conveyor belts are used, which permit a good heat transfer between the heating element and the material to be dried. When these especially thin conveyor belts are used, however, dislocation or shifting of the conveyor belt along the driving and/or deflection rollers along the conveyor device often occurs. To eliminate this dislocation and shifting, tilting mechanisms have been proposed, with which the driving and/or deflection rollers are tilted about a tilt axis extending at right angles to the roller axis. In cooperation with the tension of the conveyor belt, such tilting can counteract an axial displacement and to a lesser extent even dislocation of the conveyor belt along the roller axis. However, it has been found that because of the attendant extra engineering effort and expense, using these tilting mechanisms makes for inadequate operational reliability of the conveyor device.
To overcome this drawback, it has been proposed that shifting of the conveyor belt in the direction of the pivot axis of a driving and/or deflection roller be counteracted by an axial displacement of the roller itself. However, it has then proved disadvantageous that an axial displacement of rotatably supported roller parts, such as shaft or axle stubs, cause high wear to the rotary bearing. When belt conveyors are used in evacuatable chambers, in which the rotary bearing is disposed on the chamber wall, it has also proved disadvantageous that the sealing action of a sealing element, which upon a rotation of the roller part received in the rotary bearing provides satisfactory sealing of the interior of the chamber from the environment, rapidly decreases upon an axial displacement of the rotatably supported roller part in the rotary bearing. This in turn leads to a marked impairment in operational reliability of such conveyor devices.
To overcome this drawback, belt conveyors intended for use in evacuatable chambers have been proposed that have a driving and/or deflection roller; one roller part is held rotatably via axle or shaft stubs but fixedly in the axial direction in opposed chamber walls, and one roller part is mounted axially displaceably on the roller part that is fixed in the axial direction. In a belt conveyor of this type, disclosed in German Patent DE 31 52 151 C2, the axially displaceable roller part is in the form of a circular- cylindrical jacket-segmental half shell, which is retained on the axle or shaft stubs by retaining rings.
In this latter reference, but also in U.S. Pat. No. 3,743,152, conveyor devices of the type described are disclosed in which bars are provided, which are secured axially displaceably on the axially fixed roller part. In these belt conveyors, the axial displacement of the axially displaceable roller parts is accomplished with adjusting elements, in the form of pneumatic cylinders or electrical or mechanical means to displace, which are disposed inside the evacuatable chamber. On the one hand, this increases the total volume to be evacuated, and on the other it impairs the operational reliability, because leaks from pneumatic cylinders that can be used as the adjusting element can increase the pressure inside the evacuatable chamber; corrections initiated from outside via mechanical linkages are complicated and expensive and can also lead to sealing problems, and if electrical adjusting elements are used, handling products containing explosive volatile components is risky from the standpoint of safety. Overall, the known belt conveyors are thus functionally relatively unsafe and unreliable, and problems repeatedly occur during operation.
In view of the above-explained problems in the prior art, the object of this invention is to disclose a structurally simple conveyor device which assures high operational reliability and functional safety.
According to the invention, this object attained by a conveyor device of the type defined at the outset, which is substantially characterized in that the rotary bearing has a bearing part that is rotatable about the, axis of the roller held therein and the roller held on the rotary bearing is provided with a structural component which penetrates the rotary bearing and is coupled to the bearing part in a manner fixed against relative rotation and which is displaceable axially relative to the bearing part.
This invention is based on the recognition that the problems observed in the use of known conveyor devices with a rotary leadthrough allowing an axial displacement, that is, problems of durability of the rotary leadthrough and of the sealing action of sealing elements associated with the rotary leadthrough, can be solved by decoupling the axial displacement of the roller, or a roller part, from the rotary motion. With the conveyor device of the invention, this decoupling is accomplished by providing the rotary bearing with, a bearing part that is rotatable about the axis of the roller retained thereon, and the axial displacement is effected via a structural component that is entrained in a rotary motion of this bearing part. With this arrangement, the axial displacement of the roller, or of the axially displaceable roller part, can be initiated via the structural component that penetrates the rotary leadthrough and is thus accessible on the side of the rotary bearing away from the roller. In this way, the axial displacement of a built-in conveyor belt in an evacuatable chamber can be effected with an adjusting mechanism disposed outside the chamber, via the structural component that penetrates the rotary bearing. As a result, the volume that has to be evacuated can be reduced, and at the same time the operational reliability is increased, because except for the axially displaceable roller part, no further adjusting element has to be disposed inside the evacuatable chamber.
Particularly to eliminate dislocation of the conveyor belt, but also axial shifting of the conveyor belt relative to the rollers of the conveyor device itself, it has proved especially expedient for the roller to have at least two roller parts, forming successive outer faces of the roller in the circumferential direction, on of the faces being coupled to the axially displaceable structural component, and the other face being fixed axially relative to the rotary bearing. With this arrangement, an axial displacement relative to the roller itself can be eliminated by providing that in a phase of operation in which the outer face of the roller part that is coupled with the axially displaceable structural component does not rest on the conveyor belt, this roller part is displaced axially in the direction of displacement of the conveyor belt, while in the phase of operation. in which its outer face does contact the conveyor belt, this roller part is displaced in the opposite direction. In this respect, it has proved to be especially favorable if a sensor that detects the location of the conveyor belt and by a control unit, with which an adjusting mechanism, coupled to the structural component coupled in a manner fixed against relative rotation to the rotatable bearing part, is triggered in response to detection signals output by the sensor.
For reasons of stability, it has proved especially advantageous if th

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