Conveyors: power-driven – Conveyor section – Endless conveyor
Patent
1997-10-31
2000-06-06
Ellis, Christopher P.
Conveyors: power-driven
Conveyor section
Endless conveyor
198838, B65G 1706, B65G 1560
Patent
active
06070716&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a chain conveyor comprising a roller chain and a supporting rail for vertically supporting the roller chain. The roller chain includes a plurality of roller members which are interconnected in an articulated manner by a plurality of strap members. The roller chain further comprises means for laterally guiding the roller chain with respect to the supporting rail.
Chain conveyors of this kind are used for instance in the storage racks of rack storage facilities where they serve as a conveying means for the goods to be stored in these racks. Thereby, the conveying means usually is a conveyor chain provided with a plurality of rollers; both ends of this chain are interconnected by means of a belt member to form an endless loop. The goods to be stored are placed on pallets in most cases.
In the case, where goods have to be fed into the storage facility, i.e. have to be put into a specific rack, the pallets are placed onto the conveyor chain and pushed into the rack, e.g. by means of a fork lift truck. In the opposite case, when goods have to be removed from the rack, the fork lift truck engages the frontmost pallet and pulls it out of the rack, whereby the conveyor chain is displaced towards the end of the rack such that other pallets which have been placed previously onto the conveyor chain are moved towards the input/output end of the rack, too.
One difficulty observed in connection with such chain conveyors is, on the one hand, that the overall friction, in particular the friction of the conveyor chain with respect to the supporting rail, must be kept as low as possible. On the other hand, particularly in the case of comparatively long racks, the conveyor chain must be laterally guided as exactly as possible in order to avoid that the conveyor chain is not derailed with respect to the supporting rail and, moreover, in order that the width of the rack channel can be kept as low as possible to make the best use of the available room.
PRIOR ART
In the document WO 94/000370, corresponding to U.S. Pat. No. 5,538,384, a chain conveyor is disclosed which takes into account the aforementioned problems. For this purpose, the chain conveyor according to that document comprises a roller chain whose support rollers are interconnected in pairs on both sides by means of a pair of strap members. These strap members project downwards to such an extent that they guide the upper run of the roller chain laterally along the supporting rail. It is understood that the supporting rail must be smaller in width than the distance between the pair of strap members. The lower portion of the supporting rail is provided with a closed hollow return channel in which the lower run of the conveyor chain is received, guided and vertically supported.
A problem connected with the chain conveyor according to the above mentioned document may be seen in the fact that the lateral strap members of the roller chain must pick up both tractive forces and guide forces. If the lateral strap members are made of a material having good self-lubricating properties, for instance PTFE or polyethylene, either their tensile strength is not sufficient or they have to be designed with very large cross sectional areas with the result that the manufacturing costs are substantially increased. If these parts are made of composite materials, the manufacturing costs are even higher. On the other hand, if they are manufactured of steel, this involves the drawback that the friction between roller chain and guide rail is quite high.
This is particularly true for the lower run of the chain which is received in the closed return channel, because additionally the dead load of the roller chain has to be picked up by the lateral strap members, too. Due to the high friction values occurring between conveyor chain and supporting rail, the maximum length of such a chain conveyor is limited. Moreover, practice has shown that the frictional values are further increased by the tractive load on the strap members which simulta
REFERENCES:
patent: 3635327 (1972-01-01), Thiessen
patent: 3805947 (1974-04-01), Ward
patent: 4358010 (1982-11-01), Besch
patent: 5042647 (1991-08-01), Tyler et al.
patent: 5103968 (1992-04-01), Skarlupa
patent: 5538384 (1996-07-01), Haldimann
Crawford Gene O.
Ellis Christopher P.
Gilgen Fordersysteme AG
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