Printing – Stenciling – Stencils
Reexamination Certificate
1997-09-16
2001-02-27
Funk, Stephen R. (Department: 2854)
Printing
Stenciling
Stencils
C101SDIG029
Reexamination Certificate
active
06192795
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to printing apparatuses generally and, more particularly, but not by way of limitation, to a novel printing apparatus having independent microregistration means.
BACKGROUND OF THE INVENTION
The present invention concerns printing apparatuses in general, for example, screen printing or graphic arts apparatuses, which may include printing apparatuses of the endless chain drive, rotary, or straight path varieties.
For purposes of illustration, screen printing apparatuses are largely discussed herein, although the present invention is applicable to various other types of printing devices.
The problems associated with proper alignment between a screen registered in a screen printing apparatus and the object to be printed, such as an article of clothing, are well known. These alignment problems become exacerbated over time and increase in complexity with increasing numbers of screens used to effectuate certain designs. For example, multicolor screen printing typically involves a plurality of screens, each screen being provided with a certain design or part of a design which has a particular color associated therewith. Proper registration of each screen is important especially when an object is printed with more than one color or design. Registration may be in the x-direction (e.g. left/right), y-direction (front/back), or theta-direction (rotation about a z-axis perpendicular to the x-y plane).
As generally used herein, registration refers to the placement of individual screens each containing a color which collectively comprise the entire design in a relationship to each other so that when each screen individually transfers its color image to the substrate, the colors making up the design are in an optimum relationship to each other.
With present devices, any registration adjustment to the screen will affect all phases of alignment to various degrees because existing machines generally attempt to correct deficiencies in the position of a screen by trying to correct each of the x, y and theta adjustments at one time. Thus, any adjustment made to correct misregistration affects the entire image and typically results in numerous subsequent adjustments, almost in an iterative manner. For example, an adjustment along the y axis may unintentionally produce a misalignment in the angular orientation of the screen, thereby requiring further adjustment to the theta registration. Conversely, adjustments about the theta axis invariably affect both y and x direction positions simultaneously, thereby requiring further adjustment. Similarly, adjustments to x-registration positions will affect the theta position, which also in turn affects the y position.
OBJECTS OF THE PRESENT INVENTION
Thus, a primary object of the present invention is to provide a printing apparatus having a registration system wherein x-registration adjustments are separated from y- and theta-adjustments.
Another object of the present invention is to provide a registration system for receiving and positioning a screen which can take into account the individual characteristics of the screen for proper adjustment with respect to the printing head.
Furthermore, it is well known that after periods of use, a screen frame will develop irregularities or deformities, some of which may be on the order of magnitude of micrometers or even millimeters. For example, a screen may, after use, take on the shape of a parallelogram rather than its original square or rectangular shape, however slight the change in angle may be. By way of further example, when the screens are transported or cast aside or placed on their ends, the edges or sides of the screen frames may develop pits or burrs or other surface defects which detract from its original smooth, flat surface. Furthermore, screen fabric may lose tension after time and usage. Moreover, a screen may be improperly positioned during exposure, and/or variations may exist in a positive. Thus, the effects of one or more of these aberrations must be corrected for each screen on a printing device.
Thus, substitution of one screen, which was adequately positioned in a printing head , with another screen may result in at least a slight misregistration, even if the two screens appear to the user to be equivalent.
Therefore it is another object of the present invention to provide a registration system which positions a screen within a printing head and adjusts the screen by using fine adjustments, and to allow the removal of a screen and the return to its printing position within the printing head after being serviced, etc., while still remaining within acceptable registration tolerances.
Another object of the present invention is a preregistration system whose registration points coincide with corresponding registration points in each printing head.
Numerous known screen printing apparatuses and subsystems therefor already exist. For example , the following patents, all of which a re incorporated as if fully set out herein, describe various screen printing devices: U.S. Pat. Nos. 4,031,825; 4,407,195; 4,735,139; 4,846,058; 4,909,146; 4,938,130; 5,456,172; 5,483,882; 5,607,243, and U.S. Pat. No. Re.29206.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, w ill be elucidated in, or be apparent from, the following description and the accompanying drawing figures.
SUMMARY OF THE INVENTION
The present invention achieves the above objects among others, by providing a novel printing apparatus.
In one aspect, the present invention comprises a registration means for microregistering a screen which is disposed in a generally horizontal x-y plane within a printing device, the printing device having at least one pallet for mounting an object to be printed. The registration means includes a semi-stationary print head assembly which is selectively movable in an x-direction and which is selectively lockable at a desired print location. The print head assembly includes: screen receiving means for receiving the screen in the x-y plane, wherein angular displacement of the screen in a theta direction corresponds to rotation about a substantially vertical axis passing through the x-y plane; and screen adjustment means for adjusting the orientation of the screen within the x-y plane in at least one of linear displacement in the y-direction and angular displacement in the theta-direction. Thus, adjustment of the screen relative to the pallet in the x-direction at the desired print location is accomplished independently of adjustment of the screen in both the y-direction and the theta-direction. The screen adjustment means preferably allows linear displacement of the screen in the y-direction independently of angular displacement of in the theta-direction.
The printing device may further comprise a pallet drive means for indexing the pallet, in a generally horizontal plane, into and out of proximity with the semi-stationary print head assembly at the desired print location. A pallet drive means may selectively move the pallet in the x-direction. The pallet drive means may index the pallet around a closed loop.
The screen adjustment means most preferably comprises means for engaging the extreme ends of a side of the screen which is parallel to the x-direction, wherein each of the extreme ends of the screen is capable of being selectively moved independently of each other.
In another aspect, the present invention comprises an apparatus for microregistering a screen within a printing device, wherein the printing device has at least one pallet and a pallet drive means for indexing the pallet. The apparatus comprises a semi-stationary print head assembly which is selectively movable in an x-direction which is parallel to the path of the pallet and selectively lockable at a desired print location, the print head assembly including: means for registering the screen in a generally horizontal x-y plane, wherein angular displacement of the screen in a theta direction corresponds to rotation about a substantially vertical axi
Funk Stephen R.
Hix Corporation
Shook Hardy & Bacon L.L.P.
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