Blank stripping apparatus for rotary die cutters

Improved blank-stripping apparatus for rotary die cutters of the type which have a die cutting roll, and an anvil roll for supporting paperboard blanks against a cutting rule on the die cutting roll, includes a rotary-cam-timed valve system pressure-actuating one or more pneumatic piston and cylinder assemblies within or adjacent the cutting rule for ejecting scrap radially from the cutting rule in synchronism with rotation of the die cutting roll; after scrap ejection the valve system vents pressure so that contact with a succeeding paperboard blank and/or spring bias easily retracts the plunger to position for pneumatic actuation in the succeeding cycle of operation.

BRIEF SUMMARY OF THE INVENTION 
Apparatus for stripping scrap portions of a paperboard (corrugated board) 
blank from the die cutting rules used to cut the scrap portions in the 
blank, comprising a pair of rolls between which the blank is advanced for 
cutting the scrap portions therein, one of the rolls having the die 
cutting rules mounted thereon and the other roll comprising a resilient 
roll penetratable by the die cutting rules. A scrap ejector which may be 
mounted within the cutting rules, is pneumatically actuated following 
cutting of the scrap portions in the blank to push the scrap portions from 
the cutting rules. 
The present invention is of the type wherein the paperboard blanks are die 
cut in such manner as to leave scrap portions in the cutting rules for 
subsequent removal or stripping. Such blanks are passed between a pair of 
rolls, one of which includes die cutting rules and the other of which 
supports the blanks against the pressure of the die cutting rules. As the 
rolls rotate, scrap portions are cut in the blanks by the cutting rules, 
such rules usually forming a regular or irregular cutout in the blank. As 
the rolls rotate, the cutting rules come out of engagement with the blanks 
whereupon the scrap ejector is actuated to push the scrap portions out of 
the rules preparatory to their cutting scrap portions in a succeeding 
blank. The scrap ejector is preferably in the form of a piston within a 
housing, such piston including a plunger for pushing the scrap portions 
out of the cutting rules upon movement of the piston. Pressurized air is 
directed to one side of the piston at the time that it is desired to eject 
the scrap. 
The arrangement is such that the pistons are actuated after the cutting 
rules leave the point of tangency with the advancing blank. Air lines 
extend from the cutting rules to an air valve mounted adjacent one end of 
the die cutting roll. A cam is mounted on the end of the roll for 
engagement with the valve once for each rotation of the roll. When the cam 
actuates the valve, pressurized air flows through the air lines to the 
piston, causing the piston to move thereby moving the plunger against the 
scrap portions to push them out of the cutting rules. As the cam comes out 
of contact with the air valve, the plungers are freed to retract upon 
engagement with the scrap portion in a succeeding blank, or they may be 
spring-retracted. 
Because paperboard is substantially stiffer than sheet paper and tends to 
wedge in cutting rules in various directions, depending on die shape, it 
requires greater force, applied at selected locations, for ejection of 
scrap. Air blast alone would be unreliable as pressure-escape at the first 
edge released from the cutting rule would leave the scrap still partially 
wedged in the cutting rule. 
PRIOR ART 
U.S. Pat. No. 3,606,824 granted to L. F. Remington on Sept. 21, 1971 for 
"PRESS AND CONVEYOR WITH SELF-STRIPPING DIE" discloses apparatus to eject 
scrap from the cutting rule of a platen press in synchronism with 
retraction of the platen press. FIG. 3A shows two ejector mechanisms, each 
with a piston protruding from a cylinder with sealing means between, an 
enlargement on the protruding end of the piston for pushing scrap, and 
fluid supply means. Either type could be used in the present invention 
with suitable valving. 
Alternatively, if desired, a flexible bladder may be used in lieu of a 
piston and cylinder arrangement. The bladder may be constrained to expand 
in one direction upon application of pressurized air. Likewise, a closed 
metal or plastic bellows may be used. The bellows may be normally 
collapsed and expand upon application of pressurized air.

DETAILED DESCRIPTION 
FIG. 1 diagrams overall relations and operation of the system in an 
embodiment 10. 
Each paperboard blank B advances between a first roll means 20 or die 
cutter roll with one or more die cutting rules 22 protruding from the 
circumference and a second roll means 24 or anvil roll with resilient 
circumference 26 for supporting the paperboard blank against the pressure 
of the die cutting rule 22. One or more ejectors 28, which may be mounted 
within the die cutting rules 22, when pneumatically actuated by means to 
be described radially push the blank scrap S free of the die cutting rules 
22 and into any suitable conveyor 30 which is disposed for removal of the 
blank scrap. 
The first and second roll means 20, 24 have parallel axes 32, 34 and rotate 
substantially in synchronism (arcuate arrows). 
FIG. 2 diagrams scrap ejector 28 installation and actuation details which 
include associated fixed elements and rotating elements of the system. 
Fixed elements are main frame side plate 36 which acts as stationary 
support means for adjustably mounting cam 38 in proximity for actuating 
valve mechanism 48 carried on the die cutter roll 20. 
The remainder of the elements shown rotate with die cutter roll 20 about 
axis 32. Valve-supporting details are omitted for clarity. The opposite 
end of the assembly may be the same, or it may only mount that end of the 
die cutter roll rotatably. Element 49 is a bearing for journal 42. 
OPERATION 
In operation, compressed air or other gas from any suitable source enters 
through a conventional rotary seal (not shown) between fixed parts (not 
shown) and the first roll means 20 with which the rotary seal is coaxial, 
and passes long axial bore 40 in journal 42 and then generally radially 
outwardly through input conduit 44 and manifold 46 to valve 48. On 
reciprocation of cam-following valve stem or valve actuator 50 as it rides 
radially outward on cam surface 52, valve 48 passes compressed air through 
a first chamber 54 formed with the valve housing 56 by recess-defining 
walls 58, 60 of the spool 62. The compressed air then passes through bore 
64 and valve output conduit 66 along the periphery of the first roll means 
die board 67 to one or more scrap ejectors 28 located within each die 
cutting rule 22 at a level below which scrap S (phantom lines) wedges in 
the die cutting rule. Each scrap ejector 28 is a pneumatically powered 
assembly of housing or cylinder 68, and piston 70 with cup-shaped gasket 
77 sealing it to the inner wall of the cylinder. When powered, this 
assembly extends an end of the piston radially as a plunger and pushes 
scrap radially out of the die cutting rule 22. The piston may have an 
integral foot 72 attached by a screw 73 threaded in the plunger portion of 
the piston and holding the foot 72 against the end of the plunger portion. 
The foot provides larger-area urging of scrap. The cylinder 68 may be 
secured to the die board 67 by any suitable means, press-fit being 
indicated. Press-fitting is facilitated by the "Z"-shaped angling inwardly 
along and into the cylinder, of the connector tube 75. Valve output 
conduit 66 may pass through a notch 22' in the die cutting rule which is 
conventionally affixed to the die board 67. 
After ejection of scrap S by the mechanism, valve actuator 50 rides off cam 
surface 52 causing the valve 48 to vent compressed air in the ejector 28 
to the atmosphere through line 66, as compression spring 76 in the valve 
housing 56 axially restores valve spool 62 to a radially inward position. 
In the radially inward position the full diameter spool portion 78 of 
valve 48 closes off the compressed-air supply from manifold 46 and 
connects passage 64 with exhaust port 80, freeing the scrap ejector piston 
70 to be retracted by contact with the next-succeeding paperboard sheet at 
the begining of the next cycle of operation. The retraction is thus 
relatively low-force retraction. Retraction may be assisted by or entirely 
done by compression spring 81 between the inside of the outer end of 
cylinder 68, and the piston 70 enlarged lower end. 
FIG. 3 shows provision for adjusting actuation-phase or timing of the 
ejection system. The cam surface 52 is centered on the axis 32. It can be 
adjusted circumferentially by means of clamping screws 82 in one or more 
elongate slots 84 coaxial with the cam surface. A leading ramp 86 enables 
valve actuators to ride-out smoothly onto the cam surface and a trailing 
ramp 88 lets them ride-in smoothly when leaving the cam surface. 
To suit differing shapes and sizes of die cutting rules, various stations 
for scrap ejectors may be provided, as at the plurality of air lines 66, 
66a, 66b, 66c, 66d. Each station may have a valve with valve actuator 50. 
The valve actuators are preferably equally spaced on radii in a series and 
depending on number and proximity, may be spanned by the cam 38. The 
valves may be supplied by the compressed gas input conduit 44 through a 
valve-intake manifold 46 common to all valves, and preferably with arcuate 
shape, centered on the axis of the first roll means for efficient 
distribution and ease in balancing. 
The axis-centered disposition of cam 38 and the radial relation of each 
valve 48 and valve actuator 50 in the successive circumferential areas 
coact to assure proper synchronization of scrap ejectors. 
A short circumferential length of scrap may be ejected as a unit; lengths 
which extend across more than one of the stations may be freed at the 
leading edge first and then successively at points toward the trailing 
edge. Cam-span is sufficient to hold open the valve or valves required at 
a particular location for a time sufficient to ensure operation and 
ejection of scrap. 
A suitable valve 48 is sold by Numatics, Inc. of Highland, Mich. 48031 as 
12DAD valve No. 209-121B, a representative spool-and-sleeve valve. With 
the reciprocating actuator at a first position (maximum extension from the 
valve body) the valve will close off an intake line and vent an output 
line to the atmosphere. With the actuator in a second position farther 
into the valve body, the valve will connect in-take and output. The distal 
end of the valve actuator has an opening permitting ready bias to the 
first position by means of a compression spring in any suitable 
conventional housing. 
This invention is not to be construed as limited to the particular forms 
disclosed herein, since these are to be regarded as illustrative rather 
than restrictive. It is, therefore, to be understood that the invention 
may be practiced within the scope of the claims otherwise than as 
specifically described. For example, the invention will also work with 
steel-to-steel die cutting as well as with the resilient anvil die cutting 
described. In steel-to-steel die cutting, the supporting anvil roll is 
steel and the die cutting rules have a straight, not serrated edge. The 
rule penetrates the blank and pinches against the steel roll.