Conveyors: power-driven – Conveyor system for moving a specific load as a separate unit – System includes a load supported by a conveyor portion which...
Patent
1989-01-25
1990-07-17
Valenza, Joseph E.
Conveyors: power-driven
Conveyor system for moving a specific load as a separate unit
System includes a load supported by a conveyor portion which...
1988032, B65G 3700
Patent
active
049415638
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to a conveying device for pallets.
A conveying device of this type is disclosed in GB-A No. 869 900. In the latter, the conveying speed of the pallets can be changed at certain sections of the conveying path. For this purpose, two chain conveyors driven at different speeds are provided, whereof one, which travels at the basic speed, extends over the entire conveying path, whereas the second, which travels at the higher speed, is provided solely in short acceleration sections. This second conveyor can be raised by hydraulic cylinders, so that it then lifts the pallets from the first conveyor and continues to move them at its higher speed.
This known conveying device is mechanically complicated and is not suitable for flexible use on variable production lines, since the points at which the speed variation takes place, cannot be re-programmed at little expenditure.
Conveying devices are also known which have two conveying chains extending parallel to each other, in which yoke-like support caps are fitted on the individual chain links so that their upper sides form a smooth, continuous conveying surface. The feet of pallets are seated on these conveying surfaces under the weight of the pallet and are entrained by frictional resistance. If the pallet strikes against an obstacle, for example the end of a queue of pallets waiting in front of a processing station, the conveying chains may slide through under the feet of the pallets. Since the working stations set up on production lines provided with such conveying devices contain very expensive processing machines, however the travelling speed of the endless conveyors must take into account the processing time of the work-pieces in a station, it has already been proposed to reduce the unprofitable feed times of the working stations due to the fact that the pallets are drawn into the working stations and pushed out of them quickly by a separate driving device. Auxiliary conveying devices of this type comprise for example Maltese-cross transmissions or similar step-by-step transmissions, their output part acting directly on the pallet. In the case of pallet dimensions which are large in practice, corresponding step-by-step transmissions in turn have large dimensions; therefore, in small working stations or when the pallets are conveyed close to the ground, they can only be located with difficulty below the conveying plane. The maintenance of these poorly accessible step-by-step transmissions is correspondingly complicated; also, in such working stations, in which metal is removed by cutting, there is a danger that chips enter the step-by-step transmissions and damage them.
The present invention intends to provide a conveying device which makes it possible to draw pallets into a working station at a speed which is greatly increased with respect to the basic conveying speed, the points of the conveying path, at which variations of speed are intended to take place, being able to be re-programmed in a simple manner.
This object is achieved according to the invention by a conveying device as described hereafter.
In the conveying device according to the invention, at least two endless conveyors travel continuously at different speeds. These endless conveyors both have a substantially closed conveying surface, thus are protected from metal chips. Seated on these conveying surfaces are the contact members of pallets, the frictional connection between the contact members and the conveying surfaces being controllable. In this way, a pallet in question can be connected optionally to an endless conveyor travelling more quickly or to an endless conveyor travelling more slowly. The masses to be accelerated or decelerated when changing the connection result solely from the pallet and the work-piece carried by the latter, whereas in step-by-step transmissions, additional masses in the transmission itself must be accelerated and decelerated. The conveying device according to the invention may also have a very low construction and no parts which are
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patent: 3929079 (1975-12-01), Eliassen
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patent: 4699266 (1987-10-01), Weiss
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Philpitt Fred
Valenza Joseph E.
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