Printing – Stenciling – Traveling-inker machines
Reexamination Certificate
2000-02-15
2001-05-29
Yan, Ren (Department: 2854)
Printing
Stenciling
Traveling-inker machines
C101S038100
Reexamination Certificate
active
06237486
ABSTRACT:
BACKGROUND
A common method for decorating the underside portion of a skateboard deck is screen-printing. Typically, skateboards are decorated with a screen print covering the entire underside of a deck, which is referred to as “a full pass”. On top of the full pass are applied consecutive prints of different colors and patterns. This screen-printing process requires that the ink must cure before the consecutive prints can be applied. After each print, the deck is removed from a screen press and placed in a drying rack.
A particular deck, commonly known as a short board, is manufactured using plywood laminates. The laminates are formed in a molded press into a shape comprised of three basic sections, which are the nose, tail, and mid-sections. The mid-section is relatively flat but the nose and tail sections are bent at a 12-degree angle. An irregular shaped printing screen is necessary to compensate for these two angles. The curvature of the screen must closely follow the contour of the skateboard in order to successfully print. There are many complications and drawbacks that occur as a result of using curved screens. Since curved screens are not commercially available, screens must be fabricated in house. Preparing a curved screen for printing is more difficult than preparing standard flat screens because of the curvatures. A common problem with curved screens is that fabric tension is difficult to maintain when the screen has straight and curved sections. Poor fabric tension results in inferior print quality and registration. Another problem is that decks come in different sizes and shapes, which further adds to the complexity of printing. Separate screen shapes are necessary for different deck shapes.
By far the most popular skateboard shape is the short board. The short board is fabricated in a molded fashion, which includes a concave shaped mid-section with a bent nose and tail section. Screen-printing this shape by hand requires that the printer must adjust the squeegee through three different angles to complete a full pass. In addition, the printer must push down on both ends of the squeegee rubber to compensate for the concave mid-section. The pushing down on the squeegee rubber ends results in the screen mesh stretching to the immediate shape of the squeegee. The squeegee rubber becomes thereby curved. This type of hand printing requires a skill and is very tiring.
Another drawback of hand printing short boards is that ink smears around the edges of the deck making the quality of the print diminished. The smeared ink is left to dry and is scraped off at a later time using a scraping tool. This phenomena is known as “scrapping the decks”. Scrapping adds considerable time and cost to the printing process.
OBJECT AND ADVANTAGES
The present invention is a multi-color automatic screen printing apparatus for short boards utilizing a multiple of UV cure stations between successive print heads with a conveying system for transporting short boards. The first of several objectives is to overcome the difficulties of using the curved screen. Another is to overcome the difficulty of printing the concave mid-section of the deck. Another objective is to eliminate the scraping-phase and slow drying phases of printing skateboards. Obviously, dramatically increased production rates would result from the use of this invention as well as improved print quality.
SUMMARY OF THE INVENTION
A short board deck is basically a three-sided object. The tail, mid, and nose sections. The nose and tail sections are relatively flat and the mid section assumes a concave shape. The nose and tail sections are also bent to a predetermined angle relative to the mid section. Screen-printing this particular shape can be achieved by several means. Following is a method for automated printing of short boards. This process is understood to have variations and is used mainly for explaining of the invention. The process begins at a loading station shown in
FIG. 1
where L is a loading/unloading station. A deck is placed in a fixture F which has means to hold a deck D in registration from station to station. A swing arm conveyor A
1
transports the deck fixture F from the loading station L to a position of alignment where a secondary linear conveyor C transports the deck fixture to a first print station. P A typical print station P is provided with a squeegee and a flood means
60
, which travel horizontally over a flat stationary screen. S.
During the printing process, the deck D rocks under a screen S to provide a parallel platform for the squeegee during printing. A typical rocking sequence is shown in
FIG. 2
where a screen S is in a non-movable registered position. The printing sequence begins with either the nose section N or the tail section T is made parallel to the underside of the screen as shown in
FIG. 2
a.
When the squeegee G arrives at either axis point X or at axis point Y, the deck quickly rocks to maintain parallelism with the screen as shown in
FIG. 2
b
and
c.
In this fashion the deck always remains parallel to the screen with respect to the squeegee. Rotational movement must be timed to occur as the squeegee travels to the top of the bends in the deck which are located at points X, Y. Axis points X, Y are located directly at the bends in the deck and at the print surface. If these axis points are moved out of this position then the printed image will smudge because of movement between the screen and the deck.
This rocking method may seem similar to prior art. Printing round or oval objects such as bottles is generally accomplished by rotating the object and moving the screen in sequence with the squeegee remaining stationary. Such an apparatus is exemplified in U.S. Pat. No. 5,343,804, (1994) Karlyn. Other patents such as U.S. Pat. No. 5,207,156 (1993) Helling and U.S. Pat. No. 4,782,750, (1988) Marette use the same principles of rotation. A round, elliptical, or oval shaped object such as a bottle is printed using a single axis of rotation located at the center of the radius of curvature to be printed in contrast to the short board deck where the rotational movement occurs around double axis points for the printing of one side of the object. The axes are located at the bends of the deck and not the center of rotation. Another difference is that the axes of rotation are located directly at the printing surface. This provides that no movement is generated between a stationary screen and print surface during the printing and rocking process. Another important difference between prior art and the present invention is the rate of rotation. Prior art reveals that the rotation occurs continually and at a constant rate during the printing process. The rocking of a short board deck occurs suddenly as the squeegee approaches a bend in the deck. The deck is stationary during most of the printing process except for two sudden rotational movements. Another difference between the invention and prior art is made evident in the print process explained in U.S. Pat. No. 4,254,706 (1981) Lala. This exemplary machine demonstrates the ability to print in many different fashions. The squeegee, screen, and object can all be actuated. The patent text clearly states that the screen is always moved during printing objects of revolution. This is due to the fact that registration is lost if the object rotates and the screen remains stationary. The invention of this patent has the ability to print an irregular shaped object using a fixed flat screen, movable object, and a movable squeegee, however, an automatic screen printing press capable of printing short boards is described in U.S. Pat. No. 5,711,217, (1998) Boring.
This one color apparatus operates by computing vectors, which actuate motors, which move squeegee, screen, and object in programmed movements. This press is capable of printing virtually any shaped object including a skateboard with a one-color full pass however; it must be pointed out that the object of the immediate invention is to provide a multi-color press specifically for skateboards. Produci
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