Sheet folding apparatus with vacuum grip

A sequentially timed vacuum grip system holds a sheet and transports it through a folding nip defined by a pair of folding cylinders. At the nip, the folded edge of the sheet is released and simultaneously picked-up by the paired companion cylinder. Additional folds are achieved in the same manner by the use of additional cylinder pairs.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to apparatus for folding paper sheets. 
More particularly, this invention relates to a versatile apparatus and 
method capable of providing a wide variety of folds, including multiple 
folds. 
2. Description of the Prior Art 
Prior sheet folding devices typically feed a paper sheet onto cylinders 
which grip the paper using needles or folding jaws. Under high speed 
operation, however, inaccuracies in the location of the fold, as well as 
wrinkles and distortions have a tendency to occur. Prior efforts to 
control these effects, including the use of various devices to hold the 
sheets to the cylinders, have achieved only limited success. 
In one attempt to control the sheet throughout the fold (U.S. Pat. No. 
4,036,487) a folding jaw is employed with a folding blade in conjunction 
with releasable grippers, such as needles, to hold the leading and 
trailing edges of a sheet while a folding jaw grips and then draws the 
sheet off the cylinders. While this system eliminates some inaccuracies, 
it lacks speed and versatility due to its use of the mechanical folding 
jaw. 
SUMMARY OF THE INVENTION 
The objective of the present invention is to improve the speed and 
versatility of a folder while maintaining accuracy. The present invention 
achieves this objective and provides a high speed folder with a versatile 
configuration capable of achieving a variety of folds and capable of 
operating in-line or off-line. This is accomplished by the use of paired 
folding cylinders having precisely timed, sequentially controlled vacuum 
gripping and pressure release. 
The vacuum grip system holds a sheet at one or more locations while 
transporting it into a folding nip defined between a pair of folding 
cylinders. At the nip, the folded edge of the sheet is released and 
simultaneously picked-up by the paired companion cylinder. Additional 
folds are achieved in the same manner by the use of additional cylinder 
pairs. Finally, either horizontal or vertical release is available by 
selective control of the vacuum grips and pressure release.

While the invention will be described in connection with a preferred 
embodiment, it will be understood that it is not the intent to limit the 
invention to that embodiment. On the contrary, it is the intent to cover 
all alternatives, modifications, and equivalents as may be included within 
the spirit and scope of the invention as defined by the appended claims. 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning first to FIG. 1 there is shown a sheet folding apparatus and method 
employing a precision controlled vacuum grip in accordance with the 
present invention. Particularly, a pair of counter rotating cylinders 12 
and 14 are positioned with parallel axes proximate a feed of a paper sheet 
16 to receive and fold same. Sequentially controlled vacuum grips 18 and 
20 are provided on the respective cylinders to selectively grip the paper 
sheet throughout the transport and folding operation. 
The vacuum grip means generally comprises a plurality of lines of orifices 
distributed across the surface of each cylinder transverse to the 
direction of travel of the sheet. A vacuum is delivered axially to each of 
the cylinders and directed internally to selected orifices, in accordance 
with means well known to the art. While only one location (line) of vacuum 
orifices is illustrated in FIGS. 2A-2D, 3A-3K, and 4A-4C of the drawings 
and described herein, multiple lines of orifices can be activated in the 
same fashion to control any part, or all, of the sheet during its folding 
and transport. 
A basic fold operation is depicted in FIGS. 2A-2D which utilizes the pair 
of cylinders of FIG. 1. The sheet 16, having a leading edge 16a, a 
trailing edge 16b, and a previously cross-scored mid portion 16c, is fed 
from a web to first and second cylinders, 12 and 14 respectively. A 
selected line 32 of vacuum grip orifices on the first cylinder is provided 
with a vacuum induced suction precisely when the sheet reaches the 
position shown in FIG. 1A, with a selected location in the mid portion of 
the sheet aligned with the vacuum grip. This timed vacuum grip holds the 
sheet and pulls it (FIG. 2B) into the nip between the cylinders (FIG. 2C), 
causing a fold to occur. Simultaneously with the entry of the fold into 
the nip, the vacuum grip 32 on the first cylinder 12 is deactivated to 
release the sheet and the vacuum grip 34 on the second cylinder 14 is 
activated. This synchronization of the release from the first cylinder and 
the grip by the second cylinder thereby transfers the folded edge 36 of 
the sheet to the second cylinder (FIG. 2D). 
FIGS. 3A-3K depict a tri-fold achieved by use of two successive sets of 
paired cylinders. (Additional folds are achieved by utilizing additional 
paired cylinders in the same manner.) The beginning first fold is similar 
to the basic fold of FIGS. 2A-2D. Particularly, a sheet 50 (having leading 
and trailing edges 50a and 50b, and having a cross-scored mid portion 50c) 
is fed toward first 52 and second 54 upper paired cylinders. When the 
pre-selected mid portion location of the sheet 50c reaches the vacuum grip 
56 of the first upper cylinder, the grip is activated (FIG. 3A), to draw 
the sheet toward the nip (FIG. 3B) and to begin the fold. As the fold 
reaches the nip (FIG. 3C) the vacuum grip of the first upper cylinder is 
released and the vacuum grip 58 of the second upper cylinder 54 is 
simultaneously activated in synchronization with the release, thereby 
transferring the first folded edge 50d of the sheet to the second upper 
cylinder (FIG. 3D). 
The second upper cylinder now carries the sheet (FIG. 3E) to the lower 
paired cylinders (62 and 64) for a similar operation. The first folded 
edge 50d is carried by the second upper cylinder 54 past the nip with the 
first lower cylinder 62 (FIG. 3F) until a selected second mid portion 
location 50e of the sheet aligns with the vacuum grip 66 of the first 
lower cylinder 62 (FIG. 3G). Precision activation of this vacuum grip 
seizes this second mid portion location 50e of the once folded sheet (FIG. 
3G) and draws it (FIG. 3H) toward the nip between the lower cylinders, to 
create the second fold (FIG. 3I). A coincident release of the first folded 
edge (FIG. 3H) allows the sheet to slide off the second upper cylinder 54 
during the second fold, while a guide 72 positioned proximate the second 
upper cylinder maintains control of the sheet. At the nip between the 
paired lower cylinders (FIG. 3I) the vacuum grip 66 of the first lower 
cylinder is released and the grip 68 of the second lower cylinder is 
activated in synchronization with the release of the vacuum grip 66 to 
discharge the folded sheet into a horizontal orientation 70. 
Alternatively, a vertical discharge is available by omission of the final 
transfer to the second lower cylinder. 
In a further feature, the vacuum grips are selectively provided with either 
a vacuum or a pressure, to yield either a holding grip or a releasing 
push. Turning to FIGS. 4A-4C there is shown an abbreviated sequence of the 
fold of FIGS. 3A-3K, utilizing the vacuum grip with pressure release. 
Particularly, a sheet 110 is fed to the folding cylinders, as before, 
where a defined cross-scored center portion 112 is gripped by a line of 
vacuum orifices 114 on the first folding cylinder 116 (FIG. 4A). Once the 
folded edge of the sheet reaches the nip, a vacuum is applied to the line 
of orifices 118 of the second cylinder 120. To further assist the transfer 
of the sheet to the second cylinder, pressure is simultaneously provided 
to the orifices 114 of the first cylinder to provide a pressure release. 
Additional control of the sheet is obtained by means of the use of 
additional grips 122 and 124. By employing the additional vacuum grip 122 
on the first cylinder during transport of the sheet into the nip between 
the cylinders, when the first vacuum grip 114 is released, the second grip 
122 continues to carry the sheet with the first cylinder until released 
(FIG. 4B). Upon arrival of the vacuum grip 122 at the nip, a vacuum is 
provided to the second grip 124 on the second cylinder and a pressure 
release is simultaneously provided to the second grip 122 on the first 
cylinder, completing the transfer of the sheet to the second cylinder. 
In the double fold process, the second cylinder 120 continues to carry the 
sheet while a second cross-scored mid portion of the sheet is gripped and 
brought into a second nip for the second fold. As in the previously 
described embodiment, a pair of lower cylinders 130 and 132 are positioned 
to grip the sheet and carry it into the second nip for the second fold. 
Particularly, a vacuum grip 134 on the first lower cylinder 130 grips the 
second mid portion of the sheet and carries it to the second nip where it 
can be transferred to the second lower cylinder 132. This transfer is 
accomplished by applying a vacuum to the grip 136 on the second lower 
cylinder 132 and simultaneously applying a pressure to the grip 134 on the 
first lower cylinder 130. (Alternatively, the sheet can be carried through 
the nip by the first lower cylinder and released vertically by terminating 
the vacuum and applying a pressure.) 
In yet another feature (shown in FIG. 4C), as the sheet is brought into the 
second nip for the second fold, one or more grip orifices 138 on the 
second upper cylinder 120 are pressurized to provide control of the loose 
extremity 140 of the folded sheet. This provides a jet of air against the 
sheet intermediate the first and second mid portions while the sheet is 
being released from the second upper cylinder 120 and guided by the baffle 
plate 144. 
From the foregoing description, it will be apparent that modifications can 
be made to the apparatus and method for using same without departing from 
the teachings of the present invention. Particularly, while the reference 
orientation of the plurality of paired cylinders has been to upper and 
lower, the paired cylinders and the direction of the folding operation may 
be reversed, from lower to upper, or even horizontally disposed. 
Accordingly, the scope of the invention is only to be limited as 
necessitated by the accompanying claims.