Cylinder folder

In a cylinder folder for zig-zag folding a flexible web, air moves through openings in the walls of both cylinders to equalize and relieve pressure in the region between the web and the cylinders where the web is separated from the cylinders and laid down on the zig-zag stack. The air moves through the cylinder wall openings from the hollow cylinder interiors, which communicate with the ambient atmosphere through openings in the end walls of the cylinders.

CROSS REFERENCE TO RELATED APPLICATIONS 
Reference is made to co-pending U.S. application Ser. No. 730,439, filed 
Oct. 7, 1976. 
BACKGROUND OF THE INVENTION 
The present invention relates to folding apparatus, and more particularly 
to cylinder zig-zag folders such as described in U.S. Pat. No. 3,250,528, 
issued May 10, 1966 and assigned to the assignee of the present invention. 
Such folders use a pair of driven cylinders which are mounted with their 
axes of rotation in parallel adjacent relation. The outer cylindrical 
walls of the cylinders define a nip which receives the web, and gripper 
and tucker blades in the cylinder walls alternately fold and draw the web 
from the nip to deposit it in zig-zag fashion in a stack beneath the 
cylinders on a moving delivery table. 
Folding machines such as that described in the above U.S. Pat. No. 
3,250,528 have satisfactorily and accurately folded continuous, cross 
perforated webs at very high speeds. Further, since the principal motions 
are rotary, with very little reciprocating action, the theoretical maximum 
speed of operation would seem to be almost without limit. Limitations are 
imposed, however, by the paper web itself, since at higher speeds it tends 
to cling to the surfaces of the cylinders. This problem is solved in part 
by the use of stripping pins, such as the stripping pins 87 shown in the 
above-noted U.S. Pat. No. 3,250,528, which help separate the web from the 
cylinders. However, at higher speeds the tendency of the web to cling to 
the cylinders can still "bunch" or curl it in the vicinity of the 
stripping pins. 
U.S. Pat. No. 3,980,291, issued Sept. 14, 1976 and assigned to the assignee 
of the present invention, discloses a cylinder folder construction which 
improves separation of the web from the cylinders with a series of spaced 
apart shallow recesses formed around each cylinder surface. The recesses 
have bottoms slightly depressed with respect to the outer cylindrical 
walls and are separated by relatively narrow ribs which contact the web 
and form the sides of the recesses. The area of actual contact between the 
web and the cylinders is thereby substantially reduced, resulting in a 
considerably reduced tendency for the web to cling to the cylinder 
surfaces. The recesses also trap and pressurize air therein, between the 
cylinders and the web, aiding the subsequent separation thereof. 
Nevertheless, while the above inventions have successfully folded 
continuous webs at increased speeds, a need still remains to operate such 
folders at even greater speeds. Not only does this call for even better 
web separation from the cylinders, but also for better and more rapid 
stack formation. At such speeds the stack tends to "float" on air trapped 
between the folds, and to be held up by the lack of air above as the stack 
tries to settle. Sometimes this causes jams or irregular stacks as the 
folds float too close to the cylinders, or slip over one another on the 
air cushions between them. Room thus remains for improving still further 
the separation of the web from the surfaces of the cylinders and for 
facilitating proper and rapid stack formation as the web is being 
deposited at high speed in the zig-zag stack on the delivery table. 
SUMMARY OF THE INVENTION 
Briefly, the present invention provides for a positive flow or movement of 
air between the web and the cylinders at the region where the web is being 
stripped from the cylinders and laid onto the zig-zag stack. The air is 
separately available, and is independent of the surface contours of the 
cylinders themselves. The air is provided and injected principally into 
and at the site of the gap on each cylinder between it and the folded web 
as the stripping pins engage the folded web and separate it from the 
cylinders. This separately provided air, which was not previously present, 
equalizes pressure, both positive and negative, helping for example to 
break the vacuum which tends to form between the web and the cylinder as 
the stripping pins deflect the web from the cylinder. The air flows where 
needed, relieving positive pressures beneath a fold which is being 
lowered, and relieving negative pressures above that same fold. The 
cylinder will then tend much less to "overdrive" the web causing it to 
"bunch" or curl in the vicinity of the stripping pins, and the web will 
settle quickly and properly onto the stack. 
In the preferred embodiment, openings pass through the cylinder walls form 
the hollow interiors of the cylinders into the bottoms of the recesses. 
The ends of the cylinders are also open, providing passageways through the 
cylinder ends into the hollow cylinder interiors, which in turn 
communicate with the cylinder recesses through the openings through the 
cylinder walls. Thus, as the cylinders are rotated, they effectively pass 
air in whichever direction is necessary from the surrounding atmosphere 
through the cylinder ends into the interiors of the cylinders, and then 
outwardly through the openings through the cylinder walls, passing the air 
through the bottoms of the recesses. No external provision is therefore 
required for supplying the air. Instead, the cylinders are 
self-compensating as they are rotated, automatically moving the 
appropriate amounts of air in the region between the web and the cylinders 
and the web stack for aiding the release of the web as it is engaged by 
the stripping pins and equalizing and relieving pressure in this region as 
the web is being delivered to and formed into the zig-zag folded stack. 
It is therefore an object of the present invention to provide an improved 
cylinder folded construction; a cylinder folder providing for a flow of 
air in both cylinders between the region between the cylinders, the web, 
and the web stack as it is engaged by the stripper means and formed into 
the zig-zag stack; in which the air moves through openings through the 
cylinder wall; and which will provide for substantial increases in 
operating speeds for such folders in an economical, reliable, and durable 
fashion. 
Other objects and advantages of the invention will be apparent from the 
following description, the accompanying drawings and the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, which illustrate a preferred embodiment of the 
present invention, FIG. 1 shows, in a somewhat schematic manner, the 
overall construction and arrangement of the folding apparatus and the path 
of the continuous zig-zag folds 10 of a web 12 as the folds are delivered 
along the supporting top 14 of a delivery table, generally referred to as 
15. 
In FIG. 1, the web 12 of paper is shown entering the folding machine in the 
upper left-hand corner as it is received from a printing press, or the 
like, and is directed over a power-driven roller 17 downwardly into a feed 
chute 19. Commercial machines of this type are usually designed for 
processing single layer webs, although it is conceivable that the web 
could be several webs overlaid on top of one another, as is commonly used 
to form multiple-copy business forms. Either way, the webs usually have 
uniformly spaced perforations which lie transversely across the web. The 
cross perforations allow one form to be separated from an adjacent form, 
and are the lines on which the web is commonly zig-zag folded. 
A pair of folding cylinders 20 and 21 having outer cylindrical walls 22 and 
23, respectively, are driven and supported on parallel drive shafts 24 and 
25, with their axes of rotation in parallel adjacent relation. The drive 
shafts are supported in the side frames (not shown) of the folding 
apparatus in conventional fashion. The cylinders 20 and 21 and their 
cylindrical walls 22 and 23 are counter-rotated at identical peripheral 
speeds. The cylinders define a nip which receives the web from the feed 
chute 19 on its way down to the top 14 of the delivery table 15. 
Mounted longitudinally and diametrically opposite on each cylinder are 
pairs of folding jaws or grippers 28 which open and close in known fashion 
as the cylinders 20 and 21 are counter-rotated by their power source (not 
shown). Spaced 90.degree. from the grippers 28 are longitudinally disposed 
pivotable tucker blades 30. The lengthwise mounted grippers 28 and tucker 
blades 30 are mounted in the walls 22 and 23 of the cylinders with each 
gripper on one cylinder being arranged in opposed gripping relation with a 
blade on the other cylinder, and vice versa, in known fashion. As the 
cylinders rotate, the blades 30 alternately tuck the web 12, preferably at 
the cross perforations, into the grippers on alternate cylinders, and thus 
at longitudinally spaced intervals along the web. The grippers 28 then 
close on the web, and the grippers are controlled in known fashion such 
that lengths of the web are pulled away from the nip and held by the 
grippers in contact with portions of the associated outer cylindrical 
walls 22 or 23. As each gripper 28 rotates to a position opposite table 
15, it opens, releasing the web. In this way, the web is held in contact 
with a portion of the outer cylindrical wall of first one and then the 
other of the cylinders 20 and 21, and then released in this alternating 
fashion by the grippers 28, to form the zig-zag folds 10 of the web 12. 
In operation, the grippers open slightly before they are rotated to 
positions opposite the delivery table 15, so that as the web folds engage 
a series of stripping pins 35 the pins assist in removing the web from 
contact with the outer cylindrical walls 22 and 23. The stripping pins 35 
extend from outside the cylinders into recesses 37 in the outer 
cylindrical walls 22 and 23, and are positioned and operative to guide the 
folded web from the grippers and cylinders. 
The recesses 37 form a series of spaced apart shallow recesses opening 
outwardly in a circumferential direction around each cylinder, and have 
bottoms slightly depressed with respect to the outer cylindrical walls 22 
and 23. The recesses are separated by relatively narrow ribs 38 which 
contact the web 12 and form the sides of the recesses 37. As may be seen 
in FIG. 2, the area of contact between the outer cylindrical walls 22 and 
23 and the web 12 is thus limited to the small area of the ribs 38. This 
limited area of contact reduces the tendency of the web to cling to the 
cylinders after the web is released by the gripper 28 and engaged by the 
stripping pins 35. 
Although the broad recesses 37 and narrow ribs 38 facilitate release of the 
web 12 from the outer cylindrical walls 22 and 23, it has been found that 
at higher operating speeds a more satisfactory zig-zag folded web and 
stack 10 can be provided if the stripping pins 35 are further aided in 
removing the web 12 from the cylinders, and if provision is made for 
equalizing pressure within the region 40 between the nip, the web stack, 
and the cylinders, as the web is being laid down onto the stack. Thus, as 
illustrated in FIGS. 2-3, the cylinders provide for a flow of air into and 
out of their recesses 37 as the folded web is released by the grippers 28, 
guided from the cylinders by the stripping pins 35, and formed into the 
stack 10. This supply of air into the region between the web, the 
cylinders, and the stack aids the release of the web as it is engaged by 
the stripping pins and equalizes and relieves pressure in this region as 
the web is being delivered to and formed into the zig-zag folded stack. 
The cylinders 20 and 21 automatically provide their own supplies of air 
into and out of the recesses 37. The cylinders 20 and 21 have hollow 
interiors 50 and 51 respectively, and the ends 52 and 53 of the cylinders 
20 and 21 have passageways 55 therethrough which place the interiors 50 
and 51 thereof in communication with the surrounding atmosphere. The 
cylinder walls 22 and 23 have openings 60 which pass through the cylinder 
walls from the hollow cylinder interiors 50 and 51 into the bottoms of the 
recesses 37, placing the recesses in communication with the cylinder 
interiors, and these in turn with the ambient atmosphere. 
As illustrated in FIG. 2, it has been found that it is preferable to 
distribute the openings across and around each of the cylinders, but it is 
not ordinarily necessary to provide openings 60 into all of the recesses 
37. Rather, selected recesses may be so equipped, depending upon the 
nature of the web 12, the size and operating speeds of the folding 
cylinders 20 and 21, and the particular applications thereof. Variations 
may therefore be made within the scope of the present invention, according 
to the particular application at hand. 
As may be seen, therefore, the present invention provides numerous 
advantages. Principally, the present invention provides for substantial 
increases in the operating speeds of cylinder folders, with inexpensive 
and easily provided improvement thereto. As shown and described, both of 
the cylinders are provided with openings connecting their cylinder 
recesses to the interiors of the cylinders and from there to the 
atmosphere. This facilitates release of the web from the outer cylinder 
surfaces as the web is engaged by the stripping pins, and provides for a 
flow of air to equalize and relieve pressure at each cylinder and each 
side of the web stack to facilitate the rapid and proper formation 
thereof. The invention is thus inexpensive, easy to fabricate, and readily 
adaptable to many of the most popular existing cylinder folder 
configurations. 
While the form of apparatus herein described constitutes a preferred 
embodiment of this invention, it is to be understood that the invention is 
not limited to this precise form of apparatus, and that changes may be 
made therein without departing from the scope of the invention.