Conveyors: power-driven – Conveyor section – Unit load conveying surface means moved about an endless or...
Reexamination Certificate
2000-02-11
2001-08-07
Bidwell, James R. (Department: 3651)
Conveyors: power-driven
Conveyor section
Unit load conveying surface means moved about an endless or...
C198S867130
Reexamination Certificate
active
06269942
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a force transmission or transport device. As force transmission means, the device comprises a line of force transmitting elements, guide means for guiding the force transmitting elements along a redetermined course and at least one drive, whereby the drive acts upon force transmitting elements locally and displaces these in the area of the drive along the predetermined course and whereby the driven elements displace further elements in the line by pushing or pulling them.
The force transmitting elements may be connected to each other forming a chain, the connections between the elements having more or less clearance. Connected force transmitting elements can act on each other in a pulling manner, or if they have a suitable form and suitable guide means are provided, also in a pushing manner. On the other hand, the force transmitting elements may be unconnected. For unconnected force transmitting elements, it is necessary to provide guide means along the whole course (e.g. guiding channel or rails) and force transmission is only possible by means of pushing.
For transport purposes, the force transmission elements are at least partly equipped with transport means or can be coupled to such means. The transport means are e.g. grippers for gripping individual objects, loading platforms, or loading containers displaceable along the predetermined course.
Suitable drives for force transmission means as described above are, for example, sprockets meshing with the force transmitting elements or between the force transmitting elements (positive engagement) and driving these along a mostly circular section of the course.
If the force transmission means of a force transmission or transport device of the kind described above comprises mutually connected elements, with non-negligible clearance between the elements or if the force transmission means comprises unconnected elements, the distances between the elements are dependent on the load. On loaded sections of the course (e.g. between a drive and a power take-off) lines of pulled elements have the relatively largest distances between each other while lines of pushed elements have the relatively smallest distances between each other. On sections of the course where there is no load, the distances between the elements are not precisely defined and are possibly dependent on changing outer or external circumstances.
For preventing such undefined distances between force transmitting elements, force transmission means that are closed in themselves are tensioned. For example, tensioning of chains, chain adjusters, can be done with passively rotating sprung sprockets or chain channels that are elastically deformable in a longitudinal direction and designed to be slightly longer than the chain running inside them.
This kind of pre-tension between force transmission means (chain) and guide means (chain adjusters or longitudinally elastic channel) is possible only for a force transmission means which extends substantially without gaps over a predetermined course being closed in itself. It is not applicable for a force transmission means with two ends that are moved to and fro on a predetermined course. It is not applicable for a line of unconnected force transmitting elements that are displaced along a predetermined course in varying numbers. It is also not applicable for a local pretension of the force transmission means.
SUMMARY OF THE INVENTION
An object of the invention is a force transmission or transport device comprising a line of mutually connected or unconnected force transmitting elements serving as force transmission means, at least one drive acting locally on force transmitting elements, and guide means for guiding the force transmitting elements on a predetermined course. The present invention makes it possible to tension the line of force transmitting elements on at least one section of the predetermined course and, thus, to set precisely defined element distances on this section of the course. In particular, this selected tensioning is possible independent of whether the elements are connected with each other, and independent of whether the predetermined course and/or the line of force transmitting elements is closed in itself.
In accordance with the present invention, the device comprises means for tensioning the line of force transmitting elements in a predetermined section of the predetermined course by means of tractive or compressive load such that connected elements are adjusted to have the largest possible distance between each other (tractive load) or that connected or unconnected elements are adjusted to have the smallest possible distance between each other (compressive load). on one end of the section of the predetermined course on which the line of force transmitting elements is to be tensioned, a tensioning drive acting on force transmitting elements via a friction clutch is provided. On the other end of the section a further drive or an intermitting stop is provided acting on the elements substantially without slippage.
The tensioning drive drives the elements at a speed Vs different from the driving speed V of the further drive or intermitting stop (V=0) such that elements are pulled away from the further drive or stop (tractive load) by the tensioning drive or are pushed towards it (compressive load). As soon as, between the tensioning drive and the further drive, the tractive or compressive effect of the tensioning drive has built up a sufficient load in the line of elements the friction clutch of the tensioning drive starts slipping. The maximum load for tensioning the force transmission means between the tensioning drive and the further drive or stop corresponds to the friction resistance of the friction clutch of the tensioning drive.
The further drive or stop acts on the force transmitting elements substantially without slippage, i.e., by positive engagement or friction engagement such that produces slipping of the further drive only occurs with considerably larger forces than slipping of the tensioning drive.
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patent: 6019214 (2000-02-01), Herronen et al.
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patent: WO 97/15514 (1997-05-01), None
Mader Carl Conrad
Schneider Marcel
Bidwell James R.
Ferag AG
Rankin, Hill Porter & Clark LLP
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