Mechanical drive screen printing press

A screen printing press is provided having essentially three distinct power trains for accomplishing the infeed, printing and removal of stock from the printing bed, which power trains are completely mechanical in operation and are interconnected to operate in a timed relation with one another.

BACKGROUND OF THE INVENTION 
This invention relates to the field of screen printing and, more 
particularly, to a fully automatic screen printing press operated entirely 
by mechanical means. 
One known type of stencil screen printing device comprises a combined 
electro-mechanical system. Such prior art devices are sometimes referred 
to as flat bed printers and generally comprise a press head pivotally 
mounted on a fixed frame which supports a printing bed and press drive 
means. A printing screen is removably attached to a chase mounted beneath 
the press head in a position over the stock placed on the bed for 
printing. Mounted for reciprocal movement on the press head is a carriage 
assembly having a flood and squeegee bar which reciprocate across the 
screen during the printing cycle. Printing of stock is accomplished by 
lowering the carriage assembly over the stock on the printing bed, and 
reciprocating the squeegee across the screen to force ink therethrough to 
the stock. 
In some of the more sophisticated versions of flat bed printers, an 
automatic infeed and takeoff means may be provided which acts in 
cooperation with the carriage assembly and press head to simultaneously 
place new stock on the bed for printing after removing printed stock from 
the bed. It is apparent that the infeed and takeoff operation and the 
printing cycle must act in a timed relation with one another to avoid 
incomplete printing of stock and possible damage to the press. 
One of the more frequent problems encountered in known types of presses is 
the loss of synchronization between the infeed and takeoff mechanism and 
the press head. Normally, the infeed and takeoff operation is activated by 
microswitches, while the press head movement and the reciprocation of the 
carriage assembly are controlled by mechanical means. If an electrical 
failure occurred and the mechanical operation continued, the infeed 
apparatus could be located on the press bed as the press head makes its 
downward stroke, resulting in damage to the parts. To overcome this 
problem, redundant circuits or failsafe types of mechanisms have been 
proposed, but for one reason or another such systems have not proven 
entirely satisfactory. 
SUMMARY OF THE INVENTION 
Accordingly, the present invention provides an automatic press which 
includes an all-mechanical drive means for timing and synchronizing the 
infeed and takeoff operation with the printing cycle to prevent jamming or 
failure of the press. Some of the features of U.S. Pat. Nos. 3,859,917; 
3,731,623; and 4,058,307 are utilized in the present invention and said 
patents are incorporated herein by reference. 
The mechanical screen printing press of the present invention is divided 
into essentially three power trains which accomplish the three basic 
operations in screen printing. One power train raises and lowers the press 
head, a second power train reciprocates the squeegee and flood bar across 
the printing screen, and the third power train drives an infeed and 
takeoff means which removes printed stock from the bed and replaces it 
with new stock. As explained more fully below, the output shaft from a 
motor drives each of the power trains, and their operation is synchronized 
to accomplish the print, and infeed and takeoff cycles in a timed 
sequence. 
In contrast to known types of screen printing presses, the power trains of 
the present invention are entirely mechanical in operation. As mentioned 
above, the infeed and takeoff operation of many existing presses is 
controlled by electric circuitry. One problem associated with this design 
is that if an electric failure occurs, the mechanically operated print 
cycle may continue after the infeed and takeoff means has ceased 
operation. In such instances, the infeed and takeoff apparatus could be 
located on the press bed as the press head makes its downward stroke, thus 
resulting in damage to the parts. 
The present invention greatly reduces such problems associated with loss of 
synchronization by driving each of the power trains from a single drive 
shaft. In addition, each of the power trains is constructed of reliable 
mechanical parts designed for continuous operation with minimum adjustment 
and replacement necessary. 
Therefore, it is an object of this invention to provide a screen printing 
press having drive means which are entirely mechanical in operation. 
It is a further object of the present invention to provide a fully 
automated press capable of feeding, printing and removing stock using a 
mechanical drive train to perform these functions. 
It is a still further object of this invention to provide a one-way clutch 
which mechanically synchronizes the infeed and takeoff means with the 
movement of the press head and the reciprocation of the carriage assembly. 
It is another object of this invention to provide a captivated cam means 
adapted with a DC motor for reciprocation of the infeed and takeoff means 
in a timed relation with the printing function of the press. 
Further objects of the invention, together with additional features 
contributing thereto and advantages accruing therefrom, will be apparent 
from the following description of one embodiment of the invention when 
read in conjunction with the accompanying drawings wherein:

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to the drawings, and in particular, to FIG. 1, the screen 
printing press having the novel mechanical press drive means according to 
the present invention is indicated generally by reference numeral 11. The 
press 11 includes a fixed frame 13 having a control console 15 
conveniently located to enable the operator to control the press 11. 
Mounted on the top of the frame 13 is a flat printing bed 17 (see FIG. 2), 
which is preferably a vacuum base of the type utilized in U.S. Pat. No. 
4,058,307 to Bubley, et al. A vacuum source of negative pressure (not 
shown) is mounted to the frame 13 and adapted for use with the bed 17 to 
provide a suction to the printing surface 19 of bed 17 to hold stock 26 in 
a properly registered position on the bed 17 during printing. A positive 
pressure may be applied to the surface 19 to provide a blow back release 
of the stock 26 after printing, thereby facilitating removal of the stock. 
Mounted on the opposite sides of the frame 13 are a pair of bearings 20 
(one of which is not shown) which are connected by a fixed rod 21. A press 
head 23 is pivotally mounted to the fixed rod 21 for angular movement with 
respect to the printing bed 17 as discussed in detail hereinbelow. Also 
mounted near the top of frame 13 adjacent to the bed 17, are channels 24 
and 25 which are adapted with the infeed and takeoff means, discussed in 
detail below, to take unprinted stock 26 from the infeed position 27 to 
the printing surface 19 for printing, and then to remove the printed stock 
26 from the bed 17 to a stacking or delivery position 29. 
As mentioned previously, the infeed and takeoff procedure described above 
was generally accomplished in prior art devices by infeed and takeoff 
means activated by an electrical circuit including micro-switches. A 
principal feature of the present invention is that the press head 
movement, print cycle, and infeed and takeoff operations are synchronized 
in a timed sequence solely by mechanical means. As discussed more fully 
below, the present invention reduces the possibility of jamming since a 
failure in the drive train will disrupt the sequential operation of the 
press which could discontinue the entire operation. 
PRESS HEAD DRIVE TRAIN 
The drive train which raises and lowers the press head 23 is shown in 
detail in FIG. 2. The output from a variable speed DC drive motor 30 of 
any known type, is fed through a belt (not shown) to a gear reducer 31 
having an output shaft 33. An oblong-shaped head cam 35 (see FIG. 3) is 
mounted for rotation on the output shaft 33. Located rearwardly of the 
head cam 35, is a shaft 38 which extends across the width of the press 11 
and is mounted in bearings mounted on opposite sides of the frame 13. A 
cam follower arm 37 is fixedly attached at one end to shaft 38 and is 
formed with a roller 36 at the other end which rests on head cam 35 for 
movement therewith. 
A connecting rod 39 is attached at one end to the shaft 38 and moves 
angularly with the oscillation of the shaft 38. A head lifting arm 40 is 
disposed within the frame 13 and has its upper end attached to the press 
head 23 with the other end ganged to the free end of connecting rod 39. An 
identical connecting rod and head arm (not shown) are disposed on the 
opposite side of the press 11 except they are mirror images of connecting 
rod 39 and head arm 40. Thus, for purposes of description, reference 
numerals 39 and 40 will be used in connection with both pairs of 
connecting rods and head arms since they are dimensionally and 
functionally the same. 
With reference to FIG. 3, the press head 23 is raised and lowered as 
follows. The rotational output from the motor 30 rotates the head cam 35, 
which causes cam follower arm 37 to move up and down as it follows the 
oblong-shape of the head cam 35. Since the connecting rod 39 and head arms 
40 are movable with shaft 38, they too are lifted and lowered in response 
to the rotation of head cam 35. As depicted in FIG. 3, the cam follower 
arm 37 is shown in solid lines in the lower position as is the head cam 
35. As the head cam 35 rotates about the output shaft 33 to the position 
shown in dotted lines, the cam follower 37 is raised, and the connecting 
arms 39 and the head arms 40 raise the press head 23 to the position shown 
in dotted lines. When the head cam 35 returns to its original position, 
the press head 23 is slowly lowered over the printing bed 17 into position 
for the printing stroke, described below. 
As shown in FIGS. 3 and 10, press head 23 may be raised and lowered 
independently of the print and infeed and takeoff operations, for 
adjustment of the press head 23 or for cleaning. A cam 157 is operatively 
connected to the output of a DC motor 159, which is separate from and 
operable independently of motor 30. A second cam follower arm 161 attaches 
at one end to shaft 38, and is formed with a roller 163 at the other end 
which rests on cam 157 and is movable therewith. As cam 157 rotates, 
second cam follower arm 161 causes shaft 38 to rotate and connecting rod 
39 is raised and lowered in response thereto, which in turn raises and 
lowers press head 23 in the manner described above. Motor 159 may be 
stopped at any point to place press head 23 in the desired position. 
Referring now to FIGS. 11 and 12, one end of a carriage assembly 43 mounted 
for reciprocal movement on press head 23 is shown. The other side of the 
carriage assembly is a mirror image of that shown in the drawings. The 
operation and structure of the carriage assembly 43 as viewed in FIGS. 11 
and 12 is similar to that disclosed in U.S. Pat. No. 3,859,917 to Bubley 
et al., which may be referred to for a more complete discussion of the 
carriage assembly than is provided below. 
The carriage assembly 43 consists of a pair of carriage housings 46, which 
are adapted for travel along the length of press head 23 by means of 
roller bearings 47 extending outwardly from carriage housings 46 and 
disposed for movement within carriage channels 44. The carriage housings 
46 are linked to form the unitary structure of carriage assembly 43, by 
front and rear rods 41 and 42 extending between the channels 44 on either 
side of press head 23. 
The remaining structure of carriage assembly 43 consists of means for 
pivotally mounting the flood bar 62 and squeegee 61 thereto. A shuttle 53 
is provided adjacent carriage housing 46, and is supported thereagainst by 
front and rear rods 41 and 42 which ride in slots 52 formed in shuttle 53. 
Shuttle 53 is formed with a continuous Z-shaped cam track 54 which 
functions to shift the flood bar 62 and squeegee 61 in a generally 
vertical movement with respect to one another as will be discussed below. 
A movable parallelogram support 55 is mounted to the joining rods 50 and 
51 adjacent to the shuttle 53 such that the shuttle 53 is captive between 
the carriage housing 46 and parallelogram support 55. The parallelogram 
support 55 comprises top and bottom members 56 and 57 pivotally mounted 
thereon through bearing bolts 58. The opposite side members 59 and 60 of 
the parallelogram support 55 are pivotally connected to the top and bottom 
sides of the parallelogram support 55 for movement in vertically opposite 
directions. As shown in FIGS. 11 and 12, side member 59 supports the 
squeegee assembly 61 and the opposite side member 60 supports the flood 
assembly 62. 
A cam follower roller 63 is captively disposed to ride in cam track 54, and 
is attached through the vertical support member of the parallelogram 55 to 
the squeegee assembly 61. The roller 63 functions to pivot the 
parallelogram 55 about the bearing bolts 58 in response to linear movement 
of the shuttle 53 at the end of each stroke. Thus, direct movement of the 
squeegee assembly 61 with the roller 63 causes corresponding opposite 
vertical movement of the flood bar 62, providing a system in which the 
squeegee 61 and flood bar 62 are positively locked in constant 
relationship for corresponding movement. 
A stop 65 is provided at each end of the press head 23 which engages with 
the facing end of the shuttle 53 while the carriage housing 46 and the 
parallelogram 55 attached thereto continues its traverse movement, thereby 
causing the cam follower roller 63 to be moved in the cam track 54, 
shifting the parallelogram 55 and lowering the squeegee assembly 61 as 
shown in FIG. 11. At the opposite end of the press head 23 a second stop 
is provided (not shown) which engages with the shuttle 53 to reverse the 
positions of the squeegee assembly 61 and flood assembly 62 in preparation 
for the flood stroke. 
CARRIAGE ASSEMBLY DRIVE TRAIN 
A second drive train is provided by the present invention to reciprocate 
the carriage assembly 43 along the carriage channels 44 to accomplish the 
print and flood strokes in the manner described above. Referring now to 
FIG. 2, the head cam 35 mounted to output shaft 33 is ganged to a first 
drive arm 68. A second drive arm 69 is connected at one end to the first 
drive arm 68 and at the other to chain block 70 to which the ends of a 
first drive chain 71 are attached. Rotatably mounted on a countershaft 97, 
disposed at the front of press 11, is an idler sprocket 73. A lower tandem 
sprocket 80, comprising first and second lower sprockets 74 and 75 
attached together, is mounted in the lower portion of press head 23 near 
the rear of printing bed 17 (see FIG. 3). The first drive chain 71 is 
looped around the idler sprocket 73 and the first lower sprocket 74 of the 
lower tandem sprocket 80. The rotational movement of head cam 35 is 
translated into lateral movement of the first drive chain 71 and chain 
block 70 attached thereto, by first and second drive arms 68 and 69. Thus, 
lower tandem sprocket 80 and idler sprocket 73 rotate alternately in 
clockwise and counterclockwise directions in response to the back and 
forth lateral movement of first drive chain 71. (See FIG. 3). 
Referring now to FIG. 3, one side of the upper portion of the drive chain 
which reciprocates the carriage assembly 43 is shown. The opposite side of 
press head 23 is virtually identical to the structure as viewed in FIG. 3 
and all reference numerals used herein are applied to that side. 
A channel 79 is disposed near the top of the press head 23 and extends its 
entire length. A shaft 78 extending the width of press head 23, is 
rotatably mounted within channel 79. Mounted to shaft 78 is an upper 
tandem sprocket 85 comprising first and second upper sprockets 76 and 77 
ganged together. A third upper sprocket (not shown) corresponding to the 
second upper sprocket 77 of upper tandem sprocket 85, is mounted to shaft 
78 on the opposite side of press head 23 for unitary movement therewith. A 
second drive chain 81 is looped around the upper and lower tandem 
sprockets 85 and 80, attaching to the first upper sprocket 76 of upper 
tandem sprocket 85 and the second lower sprocket 75 of lower tandem 
sprocket 80. A carriage drive chain 82 extends the length of press head 23 
and loops around the second upper sprocket 77 and an idler sprocket 83 
rotatably mounted to channel 79 at the infeed end of press head 23. The 
ends of carriage drive chain 82 are attached to a chain block 84 which is 
mounted to the carriage housing 46 of carriage assembly 43 (see FIG. 12). 
Thus, a completely mechanical drive means for reciprocation of the carriage 
assembly 43 is provided consisting of a series of sprockets connected for 
synchronous motion with respect to one another by chain drives. The 
rotational movement of head cam 35 is translated into the back and forth 
lateral movement of first drive chain 71 by drive arms 68 and 69. Lower 
tandem sprocket 80 is driven by first drive chain 71, which in turn drives 
upper tandem sprocket 85. The rotational movement of upper tandem sprocket 
85 is then transferred into lateral movement of carriage drive chains 82 
which are looped around idler sprockets 83 and upper sprockets 77 
rotatably mounted on opposite sides of press head 23. The ends of carriage 
drive chains 82 attach to the housing 46 of carriage assembly 43, for 
reciprocation back and forth along press head 23. 
The raising and lowering of the press head 23 and the reciprocation of 
carriage assembly 43 occur in a timed relationship since both are 
accomplished by drive means adapted with the output shaft 33 and head cam 
35. As the press head begins to raise, parallelogram 55 is rotated to 
place the flood bar 62 in a down position and the carriage assembly 43 
travels toward the rear of the press 11 accomplishing the flood stroke. 
When press head 23 reaches the down position over the printing bed 17, 
parallelogram 55 reverses, placing the squeegee 61 in the down position, 
whereupon the carriage assembly 43 is advanced toward the front of press 
11 for the print stroke. The cycle is then repeated. 
As is well known in the art, off-contact printing is a technique wherein a 
printing screen is peeled away from the surface of bed 17 during the 
printing stroke, so that the entire screen does not rest on the stock to 
be printed causing smearing of the ink. A chase 48, pivotally mounted at 
one end to press head 23 near the front of press 11, is provided with a 
printing screen 49 removably mounted at the bottom of chase 48. As the 
squeegee 61 moves along the carriage assembly 43 during a print stroke as 
described above, the squeegee bar 61 forces ink through the screen 49 to 
the stock 26 on printing bed 17. 
It is desirable to keep the ink-soaked screen 49 from contacting stock 26 
to avoid smearing, except when the squeegee 61 forces the screen 49 into 
contact with the stock 26 during the print stroke. Accordingly, as shown 
in FIG. 7, the present invention provides a means to peel the screen 49 
away from bed 17 so that only that part of the screen 49 directly beneath 
the squeegee 61 contacts stock 26. The peeling means includes a tension 
adjustment member 251 having a spring 250 which contacts the free end of 
chase 48 and constantly urges the chase 48 upwardly from the printing bed 
17. As shown in FIG. 8, a chase alignment block 156 is mounted to carriage 
assembly 43 (see also FIG. 1), which acts as a stop to limit the vertical 
movement of chase 48 caused by spring 250, and also prevents the chase 48 
from tilting out of alignment relative to the printing bed 17 as the chase 
48 pivots upwardly. The adjustment member 251 may be adjusted to vary the 
tension of spring 250 to increase or decrease the upward force exerted on 
the chase 48. 
Opposing the upward force on chase 48 are a pair of rollers 252, one of 
which is shown in FIG. 7, which are mounted on opposite sides of carriage 
assembly 43 and contact the chase 48. As the squeegee bar 61 is advanced 
toward the front of press head 23 during the print stroke, the screen 49 
is picked up or peeled from the surface of printing bed 17 by adjustment 
member 251 as the chase 48 pivots upwardly. Smearing of ink on the newly 
printed stock 26 is thus minimized by the screen peeling means of the 
present invention, since the ink-soaked screen 49 is held away from 
printing bed 17 unless forced thereon by the squeegee bar 61 as it moves 
along the screen 49 during the print stroke. 
As mentioned above, a principal feature of the present invention is the 
operation of the infeed and takeoff apparatus by mechanical means rather 
than using a series of micro-switches as employed by certain prior art 
presses. As discussed in detail below, the infeed and takeoff operation is 
fully synchronized with the raising and lowering of press head 23 and 
reciprocation of carriage assembly 43. All three drive trains are adapted 
with the output shaft 33 to accomplish their respective functions in a 
timed relationship. 
The operation of the infeed and takeoff apparatus is described in the U.S. 
Pat. No. 4,058,307 to Bubley, et al., and reference is made thereto for a 
detailed discussion of the apparatus described in general terms below. 
Referring now to FIGS. 1 and 4, rollers 87 are mounted to the infeed and 
takeoff transfer carriage 86, and are movable within channels 24 and 25 
mounted on the frame 13 of the press 11 for lateral movement of the 
transfer carriage 86 along the length of press 11. The transfer carriage 
86 includes an elongated feed gripper 89 mounted near the infeed position 
27 as viewed in FIG. 1, and an elongated takeoff gripper 90 mounted near 
the opposite end of press 11 at the takeoff position 29. A pair of spaced 
parallel rods 91 connect the feed and takeoff grippers 89 and 90 for 
unitary movement along the length of press 11. A stabilizing track 92 (see 
FIG. 2) is mounted along the bottom surface of printing bed 17 in the 
center of press 11. A pair of bars 93 are mounted to the infeed gripper 89 
beneath the printing bed 17 perpendicular to track 92. Inwardly facing 
rollers 94 mounted on the ends of bar 93 contact track 92, and travel 
therealong with the movement of transfer carriage 86. Rollers 94 provide 
stability for the transfer carriage 86 as it travels within channels 24 
and 25 along press 11, to reduce the amount of vibration and horizontal 
shifting thereby assuring uniformity of registration of stock 26 on the 
printing bed 17. 
In operation, stock 26 to be printed is stacked on a spring-biased cam 
operated mounting plate 96, which moves horizontally and vertically 
relative to the size and amount of stock 26 to be printed. The stock 26 is 
registered to the infeed position 27 at the outside of printing bed 17 
beneath feed gripper 89, and each separate sheet is picked up from plate 
96 by a series of vacuum suction cups 88 mounted on feed gripper 89. The 
feed gripper 89 then registers the sheets to a printing position on the 
printing bed 17. As the feed gripper 89 is moving toward the printing bed 
17, the takeoff gripper 90, consisting of a pair of elongated parallel 
jaws 95 which pivot open in opposite directions, has simultaneously 
engaged and gripped a protruding edge of a sheet of printed stock and 
begun to transfer such stock to a delivery position 29. After the feeding 
and takeoff have been accomplished, the transfer carriage 86 is quickly 
returned to its initial position as the press head 23 begins its downward 
motion in preparation for the print stroke. 
Referring to FIG. 9, a no-feed indicator labeled generally as 126, is 
mounted to plate 96 at the infeed position 27. No-feed indicator 126 
consists of a feeder arm 127 mounted adjacent a switch 128 which is 
connected to the power source for drive motor 30. The feeler arm 127 
contacts the bottom of the stock of stock 26 to be printed, and is 
pressure sensitive so that it activates switch 128 when the stock 26 is 
nearly gone. When the switch 128 is activated, drive motor 30 is shut down 
to enable an operator to place more stock 26 on plate 96 for printing. 
Additionally, a stock hold down means 129 is provided having extended 
fingers 130 to prevent the stock 26 from shifting on plate 96 during the 
printing operation. 
INFEED AND TAKEOFF DRIVE MEANS 
The third mechanical drive train of the present invention for the infeed 
and takeoff operation described above is shown in FIG. 13. DC motor 30 is 
provided with a drive shaft 164 connected by a bevel gear (not shown) to 
output shaft 33 for rotation therewith. A second gear reducer 140 is 
mounted opposite motor 30 and has a shaft 165 in alignment with drive 
shaft 164 of motor 30. A bevel gear in gear reducer 140 connects shaft 165 
to an output shaft 142 for unitary movement therewith. Mounted on shafts 
164 and 165 are sprockets 167 and 168, which are connected together by a 
link chain 169. Thus, the output from motor 30 is translated from output 
shaft 33 through the cooperating sprockets 167 and 168, to the drive shaft 
142 of gear reducer 140. 
The drive shaft 142 from gear reducer 140 is connected at its free end to a 
drive cam 144 which is formed with a track 145. A drive arm 146 is 
pivotally mounted to a support member 148 positioned near the front of the 
frame 13 of press 11. A roller 149 attached to drive arm 146 is captively 
disposed within the track 145 of drive cam 144 for movement therealong. As 
the cam 144 is rotated, the roller 149 travels along the track 145 causing 
the drive arm 146 to reciprocate from the back of printing bed 17 to the 
front. 
A pair of idler sprockets 151 and 151' are mounted to opposite ends of 
printing bed 17, and are connected by a chain 152 looped around them for 
synchronous movement. The transfer carriage 86 of the infeed and takeoff 
means is connected to the free ends of chain 152 for movement therewith. A 
chain block 153 is disposed along chain 152 between idler sprockets 151 
and 151', and communicates with drive arm 146 through a connecting rod 155 
attached therebetween. 
The transfer carriage 86 is thus reciprocated along the press 11 by 
movement of drive arm 146. As cam 144 is rotated by shaft 142, the drive 
arm 146 is moved back and forth in response to the travel of roller 149 
along track 145 within cam 144. The chain 152 and transfer carriage 86 
connected thereto, are reciprocated by the connecting rod 155 which is 
attached at one end to the drive arm 146 and at the other to chain block 
153. The reciprocation of drive arm 146 is timed to correspond to the 
raising and lowering of press head 23 and to the printing cycle. The cam 
144 is formed to provide a period of dwell where the drive arm 146 remains 
stationary, during which the press head 23 is in a lowered position on the 
printing bed 17 for the print stroke. As the press head 23 is raised from 
the printing bed 17, the roller 149 reaches a point along the track 145 is 
cam 144 at which the back and forth movement of drive arm 146 is resumed. 
In response to the reciprocation of drive arm 146, the transfer carriage 
86 simultaneously removes the newly printed stock 26 from the bed 17 and 
registers a new piece of stock 26 to the bed 17 for printing, and is then 
reciprocated back to its original position as the press head 23 is lowered 
to repeat the print stroke. 
INFEED AND TAKEOFF DRIVE MEANS ALTERNATIVE EMBODIMENT 
An alternative embodiment of the mechanical drive train for the infeed and 
takeoff operation is adapted with the head cam 35 as discussed in detail 
below. Referring now to FIG. 2, the idler sprocket 73 adapted with head 
cam 35 as discussed above in connection with the carriage assembly 
reciprocation drive means, is fixedly attached to a slotted idler cam 98. 
Both idler sprocket 73 and idler cam 98 are pivotally mounted to a 
countershaft 97 which is rotatably mounted to the frame 13 at one end and 
to a bearing 99 at the other end. A slotted fixed cam 100 is mounted to 
the frame 13 adjacent idler cam 98 and concentric to countershaft 97. 
As is shown in FIG. 5, a unique one-way clutch labeled generally as 101, is 
provided by the present invention which allows the countershaft 97 to 
rotate in the counterclockwise direction only, for purposes to become 
apparent below. Clutch 101 includes a spring-biased arm 102 and a second 
arm 103 ganged together to form a right angle by pin 104. Pin 104 is 
mounted at its free end to a mounting arm 111, which is fixed to 
countershaft 97 for unitary movement of the clutch 101 therewith. A roller 
bar 105 is mounted on the free ends of arms 102 and 103, which is adapted 
to fit into slots 110 and 110' formed in the idler cam 98 and fixed cam 
100, respectively, as discussed below. 
The operation of the clutch 101 is shown in FIGS. 3 and 5. As the idler 
sprocket 73 beings to rotate in a counterclockwise direction, in response 
to first drive chain 71 as discussed above, the idler cam 98 rotates 
therewith. The roller bar 105 of the spring-biased arm 102 is constantly 
urged against the outer edge of idler cam 98 and rides thereon until it 
reaches slot 110 formed in idler cam 98. The roller bar 105 of the 
spring-biased arm 102 is then forced into slot 110 of the idler cam 98, 
which disengages the roller bar 105 of second arm 103 from the slot 110' 
formed in fixed cam 100. When the spring-biased arm 102 is engaged with 
idler cam 98, the clutch 101 and countershaft 97 rotate with idler cam 98. 
Spring-biased arm 102 remains in engagement with idler cam 98 for slightly 
more than one revolution in the counterclockwise direction, allowing the 
spring-biased arm to disengage as the idler cam 98 reverses its direction 
of rotation. As the spring-biased arm 102 disengages, the second arm 102 
pivots and contacts the outer edge of fixed cam 100. As the idler cam 98 
continues its clockwise rotation, the roller bar 105 of second arm 103 
engages with the slot 110' in fixed cam 100 which holds the clutch 101 and 
countershaft 97 in a fixed position during the clockwise rotation of idler 
cam 98. 
Referring now to FIG. 6, a lock mechanism 106 is provided as a safety 
measure to assure rotation of the countershaft 97 in the counterclockwise 
direction only. The safety lock mechanism is comprised of a lock arm 107 
biased toward the countershaft 97 by a spring-biased arm 108. A stop 109 
is provided on the underside of the lock arm 107 which engages with 
countershaft 97 should it begin to move in a clockwise direction. 
Referring now to FIGS. 2 and 4, countershaft 97 attaches at its free end to 
a main feed and takeoff drive arm 112. A second drive arm 113 is attached 
at one end to main drive arm 112, and at the other end to a chain block 
115 movable along a guide arm 116 attached to the frame 13. The second 
drive arm 113 converts the rotational movement of main drive arm 112, to 
the lateral back and forth movement of chain block 115 along guide arm 
116. An idler sprocket 119 is provided which is rotatably mounted to a 
cantilever shaft 120 disposed forwardly and at the base of frame 13. A 
first drive sprocket 122 is mounted at one end of a shaft 121 which is 
disposed beneath the transfer carriage 86 rearwardly of printing bed 17, 
the shaft 121 being rotatably mounted to the frame 13 at one end and to a 
bearing at the other end. 
A first drive chain 118 is looped around idler sprocket 119 and first drive 
sprocket 122. The ends of first drive chain 118 are attached to chain 
block 115 such that lateral movement of the second drive arm 113 and the 
chain block 115 along guide arm 116 causes first drive chain 118 to move 
therewith. Thus, the back and forth lateral movement of first drive chain 
118 is converted to a clockwise and counterclockwise rotational movement 
by first drive sprocket 122 attached thereto. 
A second drive sprocket 123 is mounted opposite first drive sprocket 122 on 
shaft 121 and is movable therewith. An idler sprocket 125 is rotatably 
mounted to frame 13 at the other end of press 11 near the infeed position 
27. A transfer chain 124 is looped around idler sprocket 125 and second 
drive sprocket 123, the ends of transfer chain 124 being attached to chain 
block 126 which is mounted on the transfer carriage 86. Although the 
structure described above refers to the side of the infeed and takeoff 
transfer carriage 86 as viewed in FIG. 4, the reference numerals are 
applied to the opposite side of the transfer carriage as well which is the 
mirror image of that in FIG. 4. 
The entire feed and takeoff cycle is thus accomplished in slightly more 
than a single counterclockwise revolution of idler cam 73, in a timed 
relation with the raising and lowering of the press head 23 and 
reciprocation of carriage assembly 43. During the rotation of idler cam 98 
in the opposite or clockwise direction, the transfer carriage 86 is at 
rest and thus the operation of the infeed and takeoff drive means is 
intermittent in nature as opposed to the continuous operation of the drive 
means for the print cycle discussed above. As the clutch 101 allows the 
countershaft 97 to rotate, the rotational movement is converted by the 
drive arms 112 and 113 to a back and forth lateral movement of chain block 
115 along guide arm 116. A complete back and forth motion of chain block 
115 along guide arm 116 is accomplished in one revolution of idler cam 73. 
The lateral motion of chain block 115 is transferred by first drive chain 
118 to first drive sprocket 122 such that first drive sprocket 122 rotates 
in one direction, and then reverses its rotation as the chain block 115 is 
pulled back along guide arm 116 in the opposite direction. This 
alternating clockwise and counterclockwise rotation is transmitted to 
shaft 121 and then to the second drive sprocket 123 mounted thereto. The 
transfer carriage 86 is reciprocated along channels 24 and 25 by transfer 
chains 124 which are looped around the second drive sprockets 123 and 
idler sprockets 125, and attached to transfer carriage 86 by means of 
chain blocks 126. 
A screen printing press is thus provided in which raising and lowering of 
the press head, reciprocation of the carriage assembly, and infeed and 
takeoff of stock are all accomplished by mechanical drive means acting in 
timed synchronization from the output of a single power source. The press 
does not depend on electric circuitry to drive a portion of the press 
operation, as was the case in certain prior art devices, and thus avoids 
problems such as jamming caused by failure of one of the drive trains, 
which could severly damage a press. It will be understood from an 
examination of the foregoing that the press of the present invention may 
be fabricated without an infeed and takeoff means, using the identical 
drive means for raising and lowering the press head and reciprocating the 
carriage assembly, which would provide for manual stacking of the printed 
stock. The mechanical operation of the present invention is durable and 
reliable, and also significantly reduces the costs of fabrication, 
maintenance and adjustment of the press. 
While the invention has been described with reference to a preferred 
embodiment, it will be understood by those skilled in the art that various 
changes may be made and equivalents may be substituted for elements 
thereof without departing from the scope of the invention. In addition, 
many modifications may be made to adapt a particular situation or material 
to the teachings of the invention without departing from the essential 
scope thereof. Therefore, it is intended that the invention not be limited 
to the particular embodiment disclosed as the best mode contemplated for 
carrying out this invention, but that the invention will include all 
embodiments falling within the scope of the appended claims.