Cylinder press drive assembly

In a screen printing cylinder press, the combination comprises: PA1 a cylinder having a gripper thereon to grip a sheet, PA1 a screen printer including a movable screen printing carriage for applying ink to the sheet on the cylinder; PA1 a lever connected to the cylinder and screen printing carriage to move the same through a stroke of given length; PA1 a cam having a predetermined profiled cam surface and a cam follower for following the cam surface and connected to the lever to actuate the lever to rotate the cylinder and to reciprocate the screen printing carriage; and PA1 adjustable stroke device in said lever for adjusting the stroke of the lever from a given length of stroke, thereby changing the length amount of rotation of the cylinder and the travel of the screen printing carriage.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to screen printing, cylinder presses and more 
particularly, to drive mechanisms for driving a screen printing cylinder 
press. 
2. Description of The Prior Art 
U.S. Pat. No. 3,915,088 discloses a commonly-used drive for such screen 
printing, cylinder presses. This drive includes a rotating crank mechanism 
which is driven by a motor with the crank mechanism providing a drive for 
a lever subassembly, which turns a gear segment to rotate a gear connected 
to the cylinder A screen printing carriage has a rack which is driven by 
the gear on the cylinder to reciprocate the carriage with oscillation of 
the cylinder. A particular problem with the crank drive is that it 
provides a harmonic motion with a substantially equal percentage of the 
time being used for acceleration of the cylinder and screen printing 
carriage and for the deceleration thereof prior to reversing the direction 
of travel of the cylinder and screen printing carriage To change the 
direction of cylinder rotation and carriage travel requires overcoming 
considerable inertia. When this inertia is not smoothly overcome, there 
may be a banging or other hitting as the cylinder reverses its direction 
of rotation which may cause the screen not to be properly registered with 
respect to a prior image or to specific spot on the web. 
With a crank as in U.S. Pat. No. 3,915,088 or with a conventional cam used 
to drive a cylinder or web press, little has been accomplished in 
controlling the inertia of the cylinder and the time period for 
deceleration of the cylinder and the traveling printing screen carriage. 
The present invention is directed to providing lower inertia and a greater 
time period for slowing down and stopping the travel of the cylinder and 
screen printing carriage in cylinder presses. 
To these ends, the present invention is directed to providing a controlled 
inertia with a profiled cam drive for cylinder screen printing presses in 
which the inertia is calculated and is controlled by minimizing the 
velocity, particularly when stopping the movement of the cylinder and 
screen printing carriage in one direction and just prior to reversing 
their directions of travel in the opposite directions. This is achieved by 
providing a faster acceleration from a stopped position over a shorter 
period of time than with a crank and then, providing for a much longer 
time and a much slower movement than with a crank, resulting in a reduced 
inertia for the travel of the cylinder and printing carriage when they are 
nearing the end of their travel in one direction. 
U.S. Pat. No. 3,915,088 discloses an adjustable stroke mechanism whereby 
the length of the stroke provided by the drive may be easily adjusted to 
change the amount of rotary movement of cylinder. However, such adjustment 
is rather cumbersome. The present invention provides an improved stroke 
adjustment mechanism for cylinder presses. 
Accordingly, a general object of the present invention is to provide a new 
and improved drive for cylinder screen printing presses. 
Another and more specific object of the invention is to provide an improved 
drive having improved inertia and displacement characteristics relative to 
the harmonic accelerations and decelerations from a crank drive. 
Another object of the invention is to provide the drive mechanism with a 
new and improved stroke adjustment mechanism for cylinder screen printing 
presses.

As shown in the drawings for purposes of illustration, the invention is 
embodied in a cylinder printing press which may be of various types, some 
of which are for example, shown in U.S. Pat. No. 3,915,088. A sheet 11 to 
be printed gripped by a gripper 13 on a rotating cylinder 17. A screen 
printing carriage 14 having a screen is located above the sheet and is 
arranged for rectilinear, reciprocating travel tangentially along the 
cylinder periphery in response to cylinder rotation. As shown, the 
printing carriage has rack 16 meshed with a gear 20 on the cylinder to 
assure timed movement of each. A squeegee blade means 18 usually having a 
flood bear and a squeegee is disposed above the screen to force ink onto 
the sheet as the cylinder rotates and the screen translates beneath the 
squeegee blade during a printing operation. On a return stroke the 
squeegee blade is raised and a flood bar is lowered to spread ink for the 
next printing operation. 
A drive means for moving the screen printing carriage 14 and for rotating 
the cylinder 17 includes a motor and cam drive means for actuating a lever 
means 21 which is connected to a cam drive means 23 which is driven by a 
motor drive unit 25. Herein, the motor drive unit includes an electric 
motor 26 connected by a suitable transmission (not shown) to gear reducer 
28 having an output shaft 31 driving the rotating cam means 23 which 
oscillates the lever means 21 which has a gear segment 36 to rotate a 
pinion gear 27 which is meshed with a pinion gear which in turn is meshed 
with gear 20 fastened to the cylinder to oscillate the same. Herein, the 
illustrated lever means includes a first lever 30 which is driven by the 
cam drive means and in turn drives a push rod 32 connected at a pivot pin 
means 34 to the first lever. The push rod 32 is connected at its opposite 
end to the gear segment 36 at a pivot pin connection 38. The first lever 
30 is generally vertically disposed and is pivoted for arcuate movement 
about a lower pivot pin 40 fastened to a stationary frame member 42. A 
similar pivot pin 44 pivotally mounts the lower end of the gear segment 36 
to the stationary, horizontal frame member 42 for pivoting about the axis 
of pivot pin. The lever 30 and gear segment 36 are generally parallel and 
are generally upright and have a limited oscillatory movement. The extent 
of oscillatory movement being illustrated in FIG. 1 between the solid 
right hand position shown in FIG. 1 and a dotted left hand position 
showing the gear segment's position at the end of the printing travel. 
In some instances, where it is not desired to provide the controlled 
inertia characteristics above-described and to be described further below, 
a crank may be used to directly oscillate the first lever 30 with the 
usual harmonic motion in the conventional manner of the prior art such as 
shown for example, in U.S. Pat. No. 3,915,088. Herein, the cam means 23 
includes a rotating steel cam body 44 which is generally circular and has 
a cam profiled surface 46 which is engaged and followed by a cam follower 
48. Herein, the cam follower 48 includes a roller 49 which is mounted on a 
stub shaft 50 which extends horizontally and is fastened to the first 
lever 30 generally adjacent to the midpoint of that of the first lever. 
Thus, as the cam follower 48 is displaced by the profiled cam surface 46, 
the lever 30 will be oscillated and displaced to push the push rod 32 and 
pivot the gear segment 36. 
In accordance with the present invention, there is provided a new and 
improved stroke adjusting means 55 which allows the adjustment of the 
printing stroke so as to provide the ability to limit the stroke of the 
cylinder 17 to that desired. This adjustment may be made easily and with 
infinitely fine adjustment by turning a threaded screw 60 preferably in 
the form of an Acme screw 60 which is driven by a drive means such as a 
handle 62 fixed to the top end of the screw. The screw extends through a 
threaded block 64 mounted in a banana-shaped slot 65 in the first lever 
30. By turning the handle 62 and the screw thread 60 in one direction, the 
block 64, which is guided in guide slot 65 in the lever by slideways 68, 
moves vertically downward to move the pivot pin 34 which is mounted on the 
block 64 downwardly to vary the throw or the displacement of the push rod 
32 and the gear segment 36. The banana slot 65 is an elongated opening 
through the first lever 30 and it is made on an arc having a radius at 
about the center of the pivot pin 38 for the push rod 32 so that the 
oscillation of the point 38 remains on the same arc 70 and the movement of 
the pin 34 remains on the same arc 72. Herein, the Acme screw 60 is 
mounted for rotational movement by stationary bearing blocks 67 and 69 at 
the upper and lower ends of the slot 65. The threaded block 64 is in the 
nature of a nut and it translates along the slot as the screw is turned. 
While a manual handle 62 is illustrated to turn the screw, a motor drive 
may be substituted for the handle to provide a remote drive for the screw. 
Also, an elongated, manually turned shaft could be provided to extend from 
the manual handle to a remote location near the press operator, if so 
desired. 
The increment of adjustment made is not at the print beginning position but 
is at the end of the printing which is at the left side of FIG. 1 which is 
at the terminal portion, as shown by the phantom line 36a in FIG. 1 
showing the leftmost position that the gear segment 36 may reach before 
the gear segment reverses its direction of travel. If the stroke 
adjustment means is used to shorten the stroke, then the gear segment 36 
may be at the phantom position 36b for a shorter stroke than the position 
36a. 
In accordance with another important aspect of the present invention, the 
illustrated cam 44 is a captive cam including preferably a captive cam 
surface which is in the form of a groove 80 formed in a flat surface 82 of 
the rotating cam body 44 and in which is positioned the cam follower 48. 
The cam follower 48 is thus captive within the groove 80 and must follow 
the contour of the cam surfaces 46 which really are the radially inner and 
outer sidewalls defining the sides for the groove 80. Herein, the cam body 
44 is fixedly mounted to a central horizontal drive shaft 31 which is the 
output shaft of the speed reducer 28. The cam body is mounted for rotation 
by a bearing 84 mounted on the shaft 31. 
Herein, the cam groove surface 46 is precisely computed and curved to 
provide displacements and inertias to provide for faster acceleration and 
slower and longer decelerations of the screen printing carriage 14 before 
it reverses its direction of travel. It will be appreciated that as the 
cylinder 17 oscillates and reverses its direction of travel it must come 
to a complete stop in its one direction of rotation before accelerating to 
travel in the opposite direction of rotation. The masses for larger sizes 
of cylinders are quite large and for high speed printing the velocities 
reached may be quite high. The momentum or inertia of these cylinders and 
connected printing carriages traveling at high speed may be quite large 
because inertia includes the factor of the velocity being squared. With 
the present invention, the maximum inertia loads are calculated so as not 
to exceed a predetermined maximum inertia load and the displacement of the 
cylinder relative to time is also calculated and the profiled cam surface 
46 is generated to limit the maximum inertia and to provide a much slower 
cylinder stopping movement over a longer period of time than with the 
usual crank or single symmetrical cam of the conventional drives. The 
conventional displacement of the cylinder may be visualized by viewing the 
curve 86 in FIG. 3 which shows a vertical displacement plotted against a 
horizontal time scale. The curve 86 shows a harmonic with the maximum 
velocity occurring midway in time at the point 86c. The initial 
acceleration of the cylinder is illustrated by the slope of the curve 
section 86b which is symmetrical with the deceleration curve section 86a 
when the cylinder begins to decelerate before it stops travel in a first 
direction at point 86f. 
With the present invention, the acceleration is much quicker and over a 
shorter time period as shown by the steeper slope of the curve section 85b 
relative to the slope of the curve section 86b for a crank or conventional 
symmetrical cam. As will be explained the preferred movement includes a 
movement which, as the gear segment 36 brings the cylinder 17 to its end 
of travel in one direction is like that of a modified sine wave which has 
a very long time and flat characteristic as shown by the a curve section 
85a on a solid line curve 85. Thus, the non-symmetrical cam surface 46 
provides a shorter period of time to accelerate the cylinder 17 from the 
beginning print position, which is shown by the faster and sharper slope 
section 85b on the curve 85 relative to the conventional harmonic curve 
section 86b shown in dotted lines for a crank or the conventional cam of 
symmetrical proportions used in prior art. Also, with a conventional 
symmetrical cam or crank, the maximum velocity at point 86c on the curve 
86 occurs later in time than the corresponding maximum acceleration point 
85c for the curve 85. Because a substantially shorter period of time is 
used for acceleration to the maximum velocity at the point 85c when using 
the profiled cam 46 of this invention, there is a very substantially 
longer period of time remaining for the deceleration. It will be seen that 
the central portion or point 86c is displaced from the center or highest 
point 85c by a time displacement of approximately twenty percent or more 
which means that there will be at least an additional twenty percent more 
time for deceleration. By profiling the cam surface 46 appropriately the 
cylinder 17 can be decelerated more slowly as shown by the flattened slope 
curve section 85a. 
In accordance with an important aspect of the present invention, the 
maximum momentum forces is calculated and is limited by changing the 
various variables so that the system is not overloaded so as not to cause 
failure due to very high inertia loads being applied, particularly during 
the stopping motion. The maximum inertia used with the present invention 
is substantially lower than a similar crank operation as shown by the 
height of the respective curves 85 and 86. Also, because the maximum 
velocity is decreased with the captive and profiled cam of this invention 
versus the maximum velocity obtained with the conventional crank, there is 
less horsepower used to drive the printing means, horsepower being a 
function of velocity. Also, as will be explained, the impact force or the 
change in force is also carefully controlled to be more evenly controlled 
at various parts of the drive cycle as compared to a crank system where 
the changes in force may be quite large, as will be explained below. 
There is illustrated in FIG. 4, a sample of the groove profile cam groove 
80 which is plotted for a cam having a weight of fifty pounds and a 
specific cycling speed. Exhibit A shows a specific printout for the forces 
generated by one profiled cam to drive a screen printing press. By way of 
explanation, the press has a specific distance of 8.244001 inches from the 
pivot center of the pivot pin 40 to the center of the cam follower ball 48 
and the first lever length measured between the pivot pin 40 and the 
center of the pivot pin 34 for the push rod is 16.25 inches. The 
horizontal distance between the first lever pivot and the centerline of 
the cam shaft 31 is 6 inches and the vertical distance between the pivot 
pin 40 and the cam shaft 31 is 7.75 inches. In Table I, the amount of 
rotation is shown per degree and X and Y displacements. The "Curve" 
dimension and radius define points to be cut to define the profiled curve 
for the profiled cam surface. The "HP" designations indicate the 
horsepower being used and indicate the amount of maximum power that is 
needed to generated by the cam drive motor 26. Because velocity is a 
factor in the formula for horsepower, the HP column also gives an 
indication of velocity at each degree of rotation. The "Force" column 
lists the impact force for each degree of rotation. It is important to 
analyze the "Force" column to assure that the maximum velocities and 
forces are not too high and also to analyze that the change in force is 
relatively uniform. For instance, when initially accelerating the lever 
means 21 and the printing means 12, the last column in Table I shows an 
incremental change in Force of 22 pounds after an initial eighteen pounds 
from position 1 to position 2. Near the end of the deceleration, the force 
change in 140.degree.-144.degree. of rotation is in less than two pound 
increments and this at the end of the slope 86a shown in FIG. 3. Positions 
145 and 146 are at points 85f on the curve 85 of FIG. 3 and at this 
stopping point the force is nearly zero and the horsepower is nearly zero. 
The horsepower is not really at zero when the cylinder is rotating, but at 
very low horsepowers, the computer is programmed to print out a zero. A 
second curve similar to the curve 85 is again generated for the printing 
means as is it is moved in the reverse direction at point 147 with force 
increasing by 15 and then by increasing additional 17 pound increments. In 
the reverse direction of travel starting at position 147, there is an 
initial acceleration up the curve section 145b to the maximum force of 
182.18 at position 162. The deceleration with zero horsepower at the 
bottom of the curve 85a occurs over positions 281-299. 
TABLE I 
__________________________________________________________________________ 
EXHIBIT A, 
CAM REPORT DATE: 08-04-1988 
CYCLOID CAM 
T NUMBER # 1733021 GRPPR DRIVE CAM W/BED LIFT 
CYCLING SPEED: 1500 WEIGHT: 50 
MAXIMUM DEVIATION 7.884 
GOING UP CONSTANT VEL. DISTANCE .05 
GOING DOWN CONSTANT VEL DISTANCE .05 
RATIO START UP/FINISH UP CYCLOID .25 
RATIO START DOWN/FINISH DOWN CYCLOID .25 
MXIMUM DEVIATION 7.884 PIVOT TO BALL 8.244001 LEVER LENGTH 16.25 
START UP 0 ALL UP = 145 START DOWN = 155 ALL DOWN = 309 CRANK POSITION = 
HORIZ DIST LEVER PIVOT TO CAMSHAFT = 6 VERT DIST PIVOT TO SHAFT = 7.75 
BEARING DIAMETER = 1.25 TANGENT OF PRESS. ANGLE .7100001 
__________________________________________________________________________ 
1 ROTATION = 1 
X = 3.9994 
Y = .0698 
CURVE = -4.0036 
RADIUS = 4.000054 
HP = 0 
FORCE = 3.71 
2 ROTATION = 2 
X = 3.9979 
Y = .1396 
CURVE = -4.2825 
RADIUS = 4.000432 
HP = 0 
FORCE = 22.33 
3 ROTATION = 3.003 
X = 3.9959 
Y = .2096 
CURVE = 9.2186 
RADIUS = 4.001454 
HP = 0 
FORCE = 44.33 
4 ROTATION = 4.008 
X = 3.9936 
Y = .2798 
CURVE = 15.6839 
RADIUS = 4.003431 
HP = 0 
FORCE = 65.8 
5 ROTATION = 5.017 
X = 3.9913 
Y = .3504 
CURVE = 414.3306 
RADIUS = 4.006667 
HP = 0 
FORCE = 86.62 
6 ROTATION = 6.03 
X = 3.9892 
Y = .4214 
CURVE = -20.3466 
RADIUS = 4.011445 
HP = .001 
FORCE = 106.26 
7 ROTATION = 7.047 
X = 3.9876 
Y = .4929 
CURVE = -9.349399 
RADIUS = 4.018036 
HP = .003 
FORCE = 124.78 
8 ROTATION = 8.069 
X = 3.9868 
Y = .5652 
CURVE = -6.9759 
RADIUS = 4.026684 
HP = .006 
FORCE = 141.73 
9 ROTATION = X = 3.9868 
Y = .6384 
CURVE = -6.7782 
RADIUS = 4.037613 
HP = .01 
FORCE = 157.03 
9.097999 
10 ROTATION = 10.132 
X = 3.9878 
Y = .7126 
CURVE = 5.3369 
RADIUS = 4.051018 
HP = .015 
FORCE = 170.56 
11 ROTATION = 11.172 
X = 3.9899 
Y = .788 
CURVE = 4.9726 
RADIUS = 4.067065 
HP = .022 
FORCE = 181.95 
12 ROTATION = 12.217 
X = 3.9933 
Y = .8647 
CURVE = 4.8208 
RADIUS = 4.08589 
HP = .03 
FORCE = 191.28 
13 ROTATION = 13.269 
X = 3.9979 
Y = .9428 
CURVE = 5.4255 
RADIUS = 4.107595 
HP = .04 
FORCE = 198.31 
14 ROTATION = 14.326 
X = 4.0037 
Y = 1.0225 
CURVE = 5.6491 
RADIUS = 4.132248 
HP = .052 
FORCE = 203.03 
15 ROTATION = 15.388 
X = 4.0107 
Y = 1.1038 
CURVE = 6.0713 
RADIUS = 4.159883 
HP = .066 
FORCE = 205.33 
16 ROTATION = 16.454 
X = 4.0188 
Y = 1.1869 
CURVE = 7.0907 
RADIUS = 4.190498 
HP = .081 
FORCE = 205.23 
17 ROTATION = 17.523 
X = 4.028 
Y = 1.2718 
CURVE = 8.2937 
RADIUS = 4.224056 
HP = .097 
FORCE = 202.67 
18 ROTATION = 18.595 
X = 4.038 
Y = 1.3585 
CURVE = 12.0065 
RADIUS = 4.260485 
HP = .115 
FORCE = 197.78 
19 ROTATION = 19.668 
X = 4.0488 
Y = 1.4471 
CURVE = 15.0382 
RADIUS = 4.299681 
HP = .133 
FORCE = 190.49 
20 ROTATION = 20.742 
X = 4.06 
Y = 1.5376 
CURVE = 33.4357 
RADIUS = 4.341506 
HP = .151 
FORCE = 181.03 
21 ROTATION = 21.816 
X = 4.0716 
Y = 1.6299 
CURVE = 53.2765 
RADIUS = 4.38579 
HP = .17 
FORCE = 169.31 
22 ROTATION = 22.889 
X = 4.0833 
Y = 1.7239 
CURVE = -55.1839 
RADIUS = 4.432335 
HP = .187 
FORCE = 155.75 
23 ROTATION = 23.959 
X = 4.0948 
Y = 1.8196 
CURVE = -21.2033 
RADIUS = 4.480916 
HP = .204 
FORCE = 140.25 
24 ROTATION = 25.027 
X = 4.1058 
Y = 1.9169 
CURVE = -14.4374 
RADIUS = 4.531285 
HP = .22 
FORCE = 123.07 
25 ROTATION = 26.091 
X = 4.1161 
Y = 2.0156 
CURVE = -11.3946 
RADIUS = 4.583172 
HP = .233 
FORCE = 104.55 
26 ROTATION = 27.15 
X = 4.1254 
Y = 2.1156 
CURVE = -8.727101 
RADIUS = 4.636289 
HP = .244 
FORCE = 84.72 
27 ROTATION = 28.205 
X = 4.1333 
Y = 2.2168 
CURVE = -7.1736 
RADIUS = 4.690334 
HP = .253 
FORCE = 63.87 
28 ROTATION = 29.255 
X = 4.1397 
Y = 2.3189 
CURVE = -6.5407 
RADIUS = 4.744993 
HP = .259 
FORCE = 42.32 
29 ROTATION = 30.3 
X = 4.1442 
Y = 2.4217 
CURVE = -5.3794 
RADIUS = 4.799947 
HP = .261 
FORCE = 20.26 
30 ROTATION = 31.34 
X = 4.1465 
Y = 2.5251 
CURVE = -4.9241 
RADIUS = 4.854938 
HP = .262 
FORCE = 2.59 
31 ROTATION = 32.374 
X = 4.1467 
Y = 2.6289 
CURVE = -5.061 
RADIUS = 4.909918 
HP = .262 
FORCE = .78 
32 ROTATION = 33.403 
X = 4.1447 
Y = 2.7333 
CURVE = 6.4376 
RADIUS = 4.964865 
HP = .261 
FORCE = 2.29 
33 ROTATION = 34.427 
X = 4.1404 
Y = 2.838 
CURVE = 4.89 
RADIUS = 5.019758 
HP = .261 
FORCE = 3.61 
34 ROTATION = 35.447 
X = 4.1339 
Y = 2.943 
CURVE = 5.0575 
RADIUS = 5.074578 
HP = .26 
FORCE = 5.15 
35 ROTATION = 36.462 
X = 4.1252 
Y = 3.0483 
CURVE = 4.9473 
RADIUS = 5.129304 
HP = .259 
FORCE = 6.37 
36 ROTATION = 37.473 
X = 4.1141 
Y = 3.1538 
CURVE = 4.7906 
RADIUS = 5.183917 
HP = .258 
FORCE 
__________________________________________________________________________ 
= 7.81 
Thus, it will be seen that force applied to accelerate the printing 
carriage rises quickly from 15 position 1 in Table I to a maximum of 
205.33 at position 15 which is on the curve section 85b on the curve 85 of 
FIG. 3 and then declines from position 15 to position 145 at which the 
force is zero. It should be noted that the horsepower (HP) is reduced to 
zero as early as position 128 and remains at zero through position 151 and 
that horsepower begins to be seen again at position 152 when the carriage 
is beginning to travel in the opposite direction. At positions 145 and 
146, the printing carriage will be reversing direction and at position 300 
the carriage will be reversing its direction of travel again. FIG. 4 
illustrates an actual cam printout corresponding to the data in Table I. 
The cam profile in FIGS. 1-3 is merely representative whereas cam profile 
of FIG. 4 is an actual cam profile used on existing printing press. 
A brief description of the invention will be given illustrating th 
preferred embodiment of the invention. When the motor 26 is energized and 
the cam means 23 is beginning to be driven toward its beginning print 
position. The cam 44 turns and the cam surfaces 46 push the cam follower 
48 to accelerate the cylinder 17 and the screen printing carriage quickly 
towards its maximum velocity, this being the fast rise along the slope 
85b. Whereupon the acceleration will begin because of the curvature of the 
slot in the cam which causes the cylinder to be turned rapidly toward the 
beginning print position which is to the right, as viewed in FIG. 1, and 
after about thirty percent of its movement to the right, the acceleration 
will begin to decelerate from the point 85c on the curve 85, and then the 
deceleration continues for the remaining seventy percent of the travel to 
the right towards the beginning print position. The deceleration can be 
seen in the Table and is particularly indicated by the slower, more 
generally curved slope 85a which shows that there is substantially less 
displacement with time on the curve 85a than on the corresponding portion 
of the curve 86a which represent the deceleration in time of a typical 
crank having a harmonic motion. In the harmonic crank motion, it will be 
seen that only about fifty percent of the time is used for deceleration 
and the deceleration is much faster with higher inertias. Because inertia 
is dependent upon the velocity squared, and because with this invention 
slower velocities are now occurring at the end of the travel in one 
direction, there is a significant lessening of the inertias to be overcome 
to stop the cylinder and printing carriage and to reverse their travel 
directions. 
From the foregoing, it will be seen there has been provided a new and 
improved drive for a screen printing press and more particularly, the 
drive which has controlled inertia characteristics differing from that of 
the prior art drives. The preferred deceleration is by means of a profiled 
cam characteristic which has a very long deceleration time for the 
cylinder before a reversal of the direction of rotating travel so that 
there will be less banging or jarring motions. The present invention also 
provides a quick and easy manner in which the stroke can be adjusted so 
that it can be sized to the particular area of the web being printed. The 
stroke is adjusted at the end of the print direction travel and the 
beginning print stroke always remains at the same position. 
A preferred embodiment has been shown and described, and it will be 
understood that there is no intent to limit the invention by such 
disclosure; but, rather, it is intended to cover all modifications and 
alternate constructions falling within the scope of the invention as 
defined in the appended claims.