Indexing vacuum table

Details Indexing vacuum table Indexing vacuum table

1999-02-22

2001-05-15

Bratlie, Steven A. (Department: 3652)

Conveyors: power-driven

Conveyor section

Unit load conveying surface means moved about an endless or...

C198S689100

Reexamination Certificate

active

06230876

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a conveying system having a plurality of work platens or tables movable through successive work stations and more particularly to vacuum means for holding the work in position on the platens both in the work stations and between work stations. The invention most particularly relates to an indexed multicolor screen printer line having a work station for each color.
It is known in the screen printing art that endless conveyor means containing a plurality of work platforms or platens can be used to move the print substrate on the platens through the various screen printing stations. It is also known that the substrate to be printed can be held on the platens by a vacuum. However, problems are encountered in holding the substrate in an absolutely fixed position on the platen not only while the platens are stationary in each of the printing stations but also while the platens are in motion between stations. One solution found in the prior art is for each platen to have its own vacuum system.
However, these systems are expensive and complicated.
Another problem is that such multicolor printers have a fixed configuration with a fixed number of printing stations printing a fixed number of colors. If additional colors are to be printed, the work must be run again through the same or a different printer having the additional colors. This greatly limits productivity.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a conveying apparatus for moving a series of work platens each holding a work piece through a series of work stations including means for maintaining the work pieces in a fixed position on the platens. A further object is to provide a modular arrangement whereby the number of work stations can be easily selected and changed including concomitant changes in the means for maintaining the work piece positions.
In the present invention, an endless conveyor having a series of work platforms or platens intermittently moves each of the platens to each of a series of work stations. A vacuum is used to hold the work pieces on the platens. More specifically, in one embodiment, a series of fixed vacuum ports connects the platens to the vacuum when the platens are at rest in each work station and a series of movable vacuum ports connect the platens to the vacuum as the platens are moved from one work station to the next. The vacuum sources are switched between the movable and fixed ports as the conveyor is moved and stopped. The series of movable vacuum ports can be driven by a single drive and connected to each other in a modular mode. In a second embodiment, a series of first vacuum ports moves forward and applies the vacuum as the platens are indexed forward. Simultaneously, a series of second vacuum ports moves rearward to be ready for the next cycle.


REFERENCES:
patent: 3794151 (1974-02-01), Feasey
patent: 4188770 (1980-02-01), Tabur
patent: 4719721 (1988-01-01), Stump
patent: 4984960 (1991-01-01), Szarka

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