Machine for screen printing curved objects

A machine for screen printing curved objects has a frame with support rods and positioning rods, a scraping assembly which slides on the support rods under the influence of a motor and a gear wheel/spur rail combination, and a pair of screen-holding structures which are anchored to the positioning rods and hold a screen therebetween. The scraping assembly and the screen-holding assembly can be vertically positioned under the influence of pneumatic cylinders. A workpiece mold holds a curved workpiece such as a bowl and is rotatable under the influence of an axle and another gear wheel/spur rail combination. Three scrapers are attached to the scraping assembly. When the motor is activated, the scraping assembly moves and the workpiece mold rotates. Outside scrapers spread ink on the screen and a center scraper applies the ink to the workpiece. A proximity switch stops the motor when the scraping assembly has moved a predetermined distance. The machine preferably has two sets of scraping assemblies and two pairs of screen-holding structures.

BACKGROUND OF THE INVENTION 
The present invention relates to a screen printing machine and, more 
particularly, to a machine that is able to screen print curved or 
cylindrical objects. 
With reference to FIG. 7, a conventional machine for screen printing curved 
objects generally comprises a first pneumatic cylinder 10, a scraper means 
20, a screen holder 30, and a second pneumatic cylinder 40. The first 
pneumatic cylinder 10 actuates the scraper means 20 to move. The scraper 
means 20 comprises a pair of scrapers which are drawn over a screen held 
by the screen holder 30. The second pneumatic cylinder 40 cooperates with 
a workpiece mold to secure a workpiece in place. The workpiece has a 
curved surface. 
During operation, a screen held by the screen holder 30 is placed against a 
workpiece held by the workpiece mold and the second pneumatic cylinder 40. 
The scrapers of the scraper means 20 are drawn across the surface of the 
screen, pressing ink onto the workpiece. 
A disadvantage of this conventional design is the low production capacity 
as only one workpiece per stroke can be screen printed. Another 
disadvantage is the low quality of the print as the workpiece does not 
rotate which limits the amount of curved surface which can be printed. 
Also, the conventional machine occupies a large amount of space for the 
work capacity it can accomplish. 
Therefore, there exists a need in the field of screen printing machines for 
a machine which is able to print on the entire curved surface of a 
workpiece, which can screen print more than one workpiece at a time, and 
which does not occupy a relatively large amount of floor space. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus which is able to screen print 
two curved workpieces at a time. A frame vertically supports a scraping 
means with a pair of scraping assemblies on support rods thereof and 
horizontally supports two pairs of screen-holding means on positioning 
rods thereof. The scraping assemblies are vertically positionable on 
support means thereof, and the screen-holding means are horizontally 
positionable on the positioning rods. 
Each scraping means has a trio of scraper shelves to which a trio of 
scrapers are respectively attached. A trio of pneumatic cylinders 
respectively actuate the scraper shelves for vertical movement thereof. 
Each screen-holding means has a fixing shelf in which a securing shelf is 
vertically moveable under the influence of a pneumatic cylinder. A screen 
is fixed between respective screen-holding means by the securing shelves. 
A pair of substantially disc-shaped workpiece-holding means for retaining a 
curved workpiece apiece such as a bowl and a rotation means for providing 
rotation to the workpiece-holding means are disposed on the scraping 
means. The rotation means has an axle retained by the scraping means to 
which the workpiece-holding means are attached to respective ends thereof. 
A gear wheel is fixed to an intermediate portion of the axle and meshes 
with a horizontally-disposed spur rail. 
A motor and a translation means are further disposed on the scraping means. 
A gear wheel in direct communication with the motor meshes with another 
horizontally-disposed spur rail. Sensing means such as proximity switches 
are disposed to the frame and are in communication with the motor for 
sensing the position of the scraping means. 
In operation, workpieces are respectively mounted to the workpiece-holding 
means, being held thereon by frictional forces therebetween. Screens are 
respectively mounted between respective pairs of screen-holding means, 
being held thereon by suitable fastening means on the securing shelves. 
The pneumatic cylinders of the screen-holding means then draw the screens 
down to respectively contact the outer circumferential peripheries of the 
workpieces. The pneumatic cylinders of the scraping assemblies then extend 
a center scraper shelf and a leading-edge scraper shelf down to 
respectively contact the screens. 
After a suitable ink is applied to the screens in a conventional manner, 
the motor is activated and rotates the gear wheel communicating therewith. 
Both gear wheels mesh with respective spur rails to respectively 
horizontally move the scraping assembly and rotate the workpiece-holding 
means. The leading-edge scrapers spread the ink over the screens and the 
center scrapers applies the ink to the circumferential peripheries of the 
workpieces. 
As the scraping means nears the proximity switch, the latter stops the 
motor. The above process is then reversed accordingly for new workpieces 
in the opposite direction. 
It can be seen that the present apparatus for screen printing curved 
objects affords assemblies for screen printing two workpieces at a time 
and prints in two directions. It can be realized that the quality of the 
printing process is increased by the rotation of the workpieces and the 
disposition of the trio of scrapers. The apparatus is easily manipulated 
to accommodate different size screens and workpieces. 
Accordingly, it is a primary object of the present invention to provide an 
apparatus for screen printing curved objects which increases productivity 
and quality. 
It is another object of the present invention to provide an apparatus for 
screen printing curved objects which prints two objects at a time. 
It is still another object of the present invention to provide an apparatus 
for screen printing curved objects which prints objects in two directions. 
It is yet another object of the present invention to provide an apparatus 
for screen printing curved objects which stops the printing after a 
predetermined distance. 
It is a still further object of the present invention to provide an 
apparatus for screen printing curved objects which accommodates various 
sizes of screens and workpieces. 
These and additional objects will become apparent to a person skilled in 
the art upon reading the following detailed description with reference to 
the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS CONSTRUCTION 
Referring to the drawings, initially to FIGS. 1 to 3, a machine for screen 
printing curved or cylindrical objects is shown and generally comprises a 
frame 10, a scraping means 20, and two pairs of screen-holding means 30. 
In conjunction with the frame 10, a number of vertical supporting plates, 
such as those indicated by reference numeral 11, provide support for 
horizontally-disposed support rods 12 and positioning rods 13, as well as 
for a lower spur rail 14 and an upper spur rail 15 also disposed 
horizontally. Sensing means such as a pair of proximity switches 16 are 
provided on a top of the frame 10. 
The scraping means 20 generally comprises a vertically-disposed body 
portion which is slidably mounted on the support rods 12; a motor 21 which 
is in communication with the proximity switches 16 and is supported by the 
body portion; a translation means such as a first gear wheel 22 which is 
in direct communication with the motor 21 and meshes with the lower spur 
rail 14; a rotation means including an axle 23 which is retained by the 
body portion and a second gear wheel 24 which meshes with the upper spur 
rail 15 and is attached to the axle 23; a pair of substantially 
disc-shaped workpiece-holding means 25 each of which holds a workpiece 
thereon and is attached to a respective end of the axle 23; a pair of 
vertically-disposed support plates 26 each of which is attached to the 
body portion; and a pair of scraper assemblies 27 each of which is 
attached to and positionable on the support plates 26. 
Each scraping assembly 27 generally comprises a body portion which is 
vertically positionable on at least a pair of vertically-disposed support 
rods 271 which are attached in a spaced relationship to the support plate 
26; a trio of pneumatic cylinders 272 which are vertically disposed on the 
body portion thereof; a trio of scraper seats 273 which are vertically and 
slidably disposed in the body portion thereof and which are respectively 
actuated by the pneumatic cylinders 272; and a pair of leading-edge 
scrapers 275 and 277 and a center scraper 276 which are respectively 
attached to the scraper seats 273. 
Each screen-holding means 30 comprises a body portion with an adjusting 
screw 31 which is positionable and anchorable on the positioning rods 13; 
a fixing shelf 32 which essentially forms a horizontally-disposed part of 
the body portion thereof; a pneumatic cylinder 33 which is 
vertically-disposed on the fixing shelf; and a securing shelf 34 which is 
slidably disposed in a vertical direction on the fixing shelf 32. FIG. 3 
shows the further provision of a framed screen 40 which is placed between 
respective securing shelves 34 of the screen-holding means 30 and held 
thereon by fastening means. 
OPERATION 
With continued reference to FIGS. 1 to 3, in operation a curved workpiece 
such as a bowl, a cup, a glass, etc. is positioned on each 
workpiece-holding means 25, being held thereon by frictional forces 
therebetween. An appropriate screen 40 is secured between the 
screen-holding means 30. 
With further reference to FIG. 4, the pneumatic cylinders 33 of the 
screen-holding means 30 retract, thereby drawing the screens 40 down to 
respectively contact with under surfaces thereof the outer circumferential 
peripheries of the workpieces. 
With still further reference to FIG. 5, the pneumatic cylinders 272 of the 
scraping means 20 which correspond to scraper shelves of leading-edge 
scrapers 277 and the center scrapers 276 extend, thereby lowering 
leading-edge scrapers 277 and the center scrapers 276 down to respectively 
contact upper surfaces of the screens 40. The center scrapers 276 are 
positioned directly above the twelve o'clock positions of the 
workpiece-holding means 25. 
After a suitable ink has been applied by conventional means to the screens 
40, the motor 21 is actuated, thereby revolving the first gear 22 which 
meshes with the lower spur rail 14, such that the scraping means 20 is 
horizontally translated. As the scraping means 20 moves, leading-edge 
scrapers 277 spread the ink evenly across the upper surfaces of the 
screens 40 and the center scrapers 276 apply the ink to the workpiece. 
Also as the scraping means 20 moves, the second gear wheel 24 meshes with 
the upper spur rail 15, thereby rotating the axle 23 and the 
workpiece-holding means 25 and, consequently, the workpieces. Therefore, 
the circumferential peripheries of the workpieces are screen printed 
uniformly. 
With further reference to FIG. 6, when the scraping means 20 moves within a 
sensing distance of the proximity switch 16, the motor 21 is deactivated, 
thereby stopping movement of the scraping means 20. The placement of the 
proximity switches 16 depends upon the number of patterns on the screens 
40 to be printed, the desired number of revolutions of the workpieces, and 
the circumference of the workpieces themselves. 
To remove the printed workpieces from the workpiece-holding means 25, the 
pneumatic cylinders 272 and 33 respectively retract and extend, thereby 
raising the scraping seats 273 and the securing shelves 34, such that the 
workpieces are free for removal. 
From the position shown in FIG. 6, another pair of unprinted workpieces may 
be replaced on the workpiece-holding means 25 or the same workpieces may 
be retained while a new pair of screens 40 with different patterns is 
replaced between the securing shelves 34. The above-described operation is 
then reversed in the opposite direction, with the exception of 
leading-edge scrapers 275 spreading the ink evenly on the upper surfaces 
of the screens 40 and the center scrapers 276 applying the ink to the 
workpiece. The other proximity switch 16 stops the motor 21 when the 
scraping means 20 moves within the sensing distance, such that the 
position shown in FIG. 5 is attained once again. 
From the above, the following characteristics and variations are apparent. 
Different sized workpieces may be used with different size 
workpiece-holding means 25 as the scraping assemblies 27 are vertically 
positionable on the support rods 271. Different sized screens 40 may also 
be used as the screen-holding means 30 are positionable on the positioning 
rails 13. Furthermore (as can be particularly seen in FIG. 2), different 
sized scrapers 275, 276, and 277 may be mounted to the scraper seats 273 
depending upon the sizes of the workpieces and the screens. 
It is to be understood, however, that even though numerous characteristics 
and advantages of the present invention have been set forth in the 
foregoing description, together with details of the structure and function 
of the invention, the disclosure is illustrative only, and changes may be 
made in detail, especially in matters of shape, size, and arrangement of 
parts within the principles of the invention to the full extent indicated 
by the broad general meaning of the terms in which the appended claims are 
expressed.