Device for forming a stack on a transport table

Details Device for forming a stack on a transport table Device for forming a stack on a transport table

1997-10-20

2000-01-18

Ellis, Christopher P.

Material or article handling

Apparatus for moving intersupporting articles into, within,...

4147889, B65H 3134

Patent

active

060152575

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a device for forming a stack on a transport table.
A device of this kind is known of itself and serves for example for stacking newspapers, magazines, or the like from a so-called stacker to a shrinking station, especially for films.
As a result of the application of the binding of the magazines and insertion of uneven enclosures, such stacks of magazines, when they emerge from the stacker and during transport to the shrinking station, have a tendency to slide or even fall over. For this reason, blocking devices have already been provided that charge the two lateral areas, reducing the risk of sliding. Stacking robots can then not be used downstream from the stacker when a stack is present which has slipped and cannot be received.
The invention is based on the goal of aligning the piled stack of objects in a more stable fashion in a device according to the invention.
According to the invention, before the objects reach the stack they are charged by a separate charging device, with an opposite polarity already being present in the stack relative to the side areas of the stack that face away from one another and are charged with an electrostatic charge by the charging electrodes, said lateral areas being aligned perpendicularly to the transport direction. Since the paper stack has a dielectric constant higher than that of air, the electrical field concentrates in this area. In addition to this concentration, there is also a field concentration in the superfluous air inclusions in the stack so that the action of the field force in the stack and the accumulated charge on the surface force the air out of the stack. This results in considerably greater adhesion of the copies to one another, causing the stack to be mechanically blocked and consequently held together. This assumes that the transport table is grounded so that the electrical field is directed in the form of an arc from each lateral area to the transport table.
In an advantageous embodiment of the invention, the finished stack is not charged with a polarity by means of the two laterally disposed charging electrodes but is additionally charged on the top, which is opposite the transport table, by an additional charging electrode with reversed polarity so that the locking effect can be still further improved. Especially advantageously, the charging device has at least one endlessly circulating conveyor belt on whose upper run the objects can be supplied, and the reversal of the conveyor belt takes place on the outflow side above the transport table. The upper run of the conveyor belt has associated with it a second additional charging electrode that extends transversely to the transport direction of the conveyor belt. In addition, another endlessly circulating conveyor belt can be associated with the first conveyor belt, having its lower run associated with the upper run of the conveyor and operating at the same speed. In this way, a discharge electrode is advantageously associated with the upper run of the additional conveyor.
Further advantageous embodiments and improvements on the invention are characterized in the subclaims.
One preferred embodiment will be described in greater detail below with reference to the drawing.
FIG. 1 is a schematic top view of a device for forming a stack of magazines by means of a stacker;
FIG. 2 shows a front view of the device according to FIG. 1; and
FIG. 3 is a schematic view of the entire device.
FIG. 1 shows a blocking device 4 and a stacker, represented as a whole by 5, in schematic form. With this stacker, a stack that is represented as a whole by 6 (FIG. 2) and is composed of magazines is laid down on the transport table, represented as a whole by 7. This stack 6 is then conveyed in transport direction 8 (FIG. 1) to the next workstation, a shrinking station for example, where the stack is wrapped in film and then sealed, or shrunk by means of shrink film.
To produce a mechanical intrinsic stiffness of stack 6, the latter is blocked electrostatically. For this purpose, at the two lateral

REFERENCES:
patent: 3834290 (1974-09-01), Nelson
patent: 4765791 (1988-08-01), Brandt et al.
patent: 5062764 (1991-11-01), Welsch
patent: 5228373 (1993-07-01), Welsch
patent: 5868546 (1999-02-01), Hahne et al.

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