Printing – Stenciling – Multicolor
Reexamination Certificate
2000-06-12
2001-09-18
Yan, Ren (Department: 2854)
Printing
Stenciling
Multicolor
C101S126000
Reexamination Certificate
active
06289802
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to screen printing machines and, more particularly, to screen printing machines of the type which employ a plurality of article supports, e.g pallets or vacuum tables, for carrying articles to be printed, the article supports being displaceable around an endless path in succession through a plurality of printing stations each provided with a printing head.
2. Description of the Related Art
It has previously been known to provide a screen printing machine of the above-mentioned type having an endless chain for pulling the article supports around the endless path. Since it is important to ensure that the articles to be printed, which are carried on the article supports, are accurately located in position at the printing stations beneath the printing heads, locating devices have been provided at the printing stations for engaging and accurately positioning the vacuum tables. One such screen printing machine is disclosed in my co-pending U.S. patent application Ser. No. 08/939,497, filed Sep. 29, 1997, the disclosure of which is incorporated herein by reference.
However, it is a substantial disadvantage of chain-driven printing machines that the drive chain, over the course of time, tends to stretch, causing inaccuracy and possible disruption of the printing process.
It is also well known in the art to employ vacuum tables for supporting paper, plastic and other articles, known as flat stock, as the vacuum tables are advanced from station to station around an endless path.
It is an object of the present invention to provide a printing machine having a novel and improved mechanism for displacing the article supports for the articles to be printed to successive printing stations.
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention, a screen printing machine has a displacement mechanism which is provided for displacing a plurality of article supports in succession around an endless path of travel, with printing stations distributed along the path and each having a printing head. The displacement mechanism comprises drive members engageable with the article supports for displacing the article supports along the path, a reciprocating drive operable to reciprocate the drive members to and fro along the path and actuating devices for moving the drive members into and out of engagement with the article supports.
By the to-and-fro movement of the drive members, the article supports are advanced in succession to the printing stations, at which printing on the article supports is performed.
By using the reciprocating drive, the present invention avoids the disadvantages of prior art endless chain drives from displacing articles to successive printing stations.
The reciprocating drive preferably comprises elongate members and pivots connecting the elongate drive members, the elongate drive members and the pivots forming a drive connection between the prime mover and the drive members.
In a preferred embodiment of the invention, the endless path includes a pair of parallel elongate straight path sections, tracks extending along the straight path sections and a pair of carriages carried on the tracks, the drive members being mounted on the tracks and the reciprocating drive being connected to the carriages for displacing the carriages to and fro, in opposite directions, to one another, along the tracks.
The drive members are arranged in pairs spaced apart transversely of the path and each of the supports has leading and trailing pairs of projections to facilitate transfer of the article supports between the straight path sections.
In an alternative embodiment of this invention, an improved vacuum delivery system provides the vacuum tables with continuous access to an endless vacuum duct.
REFERENCES:
patent: 4909146 (1990-03-01), Szarka
patent: 5031527 (1991-07-01), Eppinger
Trempus Thomas R.
Yan Ren
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