Device for folding a sheet successively in two directions at right angles relative to one another

A folding device includes one folding station in which a sheet can be folded zig-zag consecutively along a first dimension and in a second direction at right angles to said first dimensions. A control device automatically sets the folding device to a first folding program intended for folding an unfolded sheet, or a second folding program intended for folding a sheet already folded in one direction.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sheet folding apparatus, and more 
specifically, to a device for folding sheets successively along a first 
dimension and in a second direction at right angles to said first 
dimension. 
2. Discussion of Related Art 
German patent application 21 52 078 discloses a folding device for folding 
sheets in two directions. In the device described therein, a sheet can be 
folded in two directions by first feeding the unfolded sheet via the feed 
path to the folding station in order to fold the sheet in one direction, 
and then feed the folded sheet again via the feed path to the same folding 
station to fold the sheet in the other direction. 
When folding large sheets of drawings, it is customary to form a folded 
drawing packet in a format whose length differs from the width, as in the 
case of the standard A4 format. To achieve this with the known device 
comprising one folding station, the folding station must be set to 
different folding distances during folding in one direction than folding 
in the other direction. Errors can easily occur as a result if the device 
operator forgets to make the correct adjustments at the right times, e.g. 
if, after a sheet has been folded in the first direction, he forgets to 
make the folding station adjustment to folding in the second direction and 
if, after the sheet has been folded in the second direction, he forgets to 
reset the folding station. A result of such lack of attention is 
incorrectly folded packets. Since folds once made are permanently present, 
it is not easily possible to make a properly folded packet from a wrongly 
folded packet. 
SUMMARY OF THE INVENTION 
Therefore, it is an object of the present invention to provide a sheet 
folding apparatus which will overcome the above noted disadvantages. 
It is a further object of the present invention to provide a sheet folding 
apparatus wherein sheets may be successively folded in two directions at 
right angles one to the other. 
The foregoing objects and others are accomplished according to the present 
invention, generally speaking, by providing a folding device comprising a 
folding station for folding a sheet in one direction and a feed path for 
feeding an unfolded sheet or a sheet folded in one direction to the same 
folding station. The feed path contains sheet-presence detection means 
which, as considered in a direction transverse to the feed direction, are 
disposed outside a part of the feed path specified for the supply of a 
sheet folded in one direction and control means which, in response to the 
reception of a detection signal from the sheet-presence detection means, 
adjust the folding station to a first folding program intended for folding 
an unfolded sheet and which, in response to the absence of a detection 
signal from the sheet-presence detection means, sets the folding station 
to a second folding program intended for folding a sheet folded in one 
direction in a direction at right angles thereto. As a result, drawings 
are obtained which are automatically folded correctly and time is saved by 
dispensing with adjustments which depend on the form of the sheet of 
drawing to be supplied, i.e., unfolded or folded in one direction. 
In a further advantageous embodiment of the device according to the present 
invention, the above specified part of the feed path is situated on one 
side of the feed path and the sheet-presence detection means comprise a 
sheet-presence detector which, as considered in a direction transverse to 
the feed direction, is situated at a distance from the side greater than 
the maximum width to which a sheet can be folded according to the first 
folding program and which is smaller than the minimum width of an unfolded 
sheet which is supplied along the feed path and which can be folded in 
accordance with the first folding program. Consequently, just one 
sheet-presence detector is sufficient; therefore it is a simple matter for 
the control means to process the detection signals. 
If the sheet-presence detector is at a distance from the common side of the 
feed path which is nearer to the minimum width than to the maximum width, 
then automatic adjustment to the second folding program is less sensitive 
to accurate feeding of a sheet folded in one direction, e.g. if such a 
sheet is not moved correctly along the side of the feed path, something 
which would otherwise readily cause a sheet folded in one direction to 
activate the presence detector, so that the folding station would be 
incorrectly set to a first folding program.

DETAILED DISCUSSION OF THE INVENTION 
The device illustrated in FIGS. 1 and 2 comprises a folding station 1 for 
the zig-zag folding of a sheet supplied via entry table 2. The folding 
station 1 is of the type illustrated in UK patent 1 394 480 and comprises 
a pair of folding rollers 3 and 4 and a pair of folding rollers 5 and 6, 
the pairs of rollers forming folding nips 8 and 9 respectively at some 
distance from one another in a folding plane 7. 
The direction of rotation of the jointly driven folding rollers 3-6 is 
reversible. Transport rollers 11 and 12, the construction of which will be 
described hereinafter, form a transport nip 13 in a path portion 14 
extending at right angles to the folding plane 7. A funnel-shaped 
sheet-guide member 16 is disposed in the zone between the transport nip 13 
and the folding nips 8 and 9 and is movable between a position in which a 
sheet fed through the transport nip 13 is conveyed in the direction of 
folding nip 8, and a position in which the sheet fed through transport nip 
13 is conveyed in the direction of folding nip 9. 
To form a fold in a sheet which is fed by transport nip 13 with its leading 
edge between folding rollers 3 and 4 which are initially free of one 
another but are driven in the sheet transport direction, the direction of 
rotation of all of the folding rollers 3-6 is reversed and the sheet guide 
member 16 is moved into a position in which the sheet is fed to the 
folding nip 9. As a result, a loop is formed in the sheet in the space 
beneath the sheet guide member 16. When this loop is engaged by the 
folding nip 9, a fold forms in the sheet at that place. By moving the 
sheet guide member 16 back again and reversing the direction of rotation 
of the folding rollers 3-6, while the sheet is still fed through the 
transport nip 13, a second fold is formed in the sheet in opposition to 
the first fold. By repeating the reversal of the movement of the folding 
rollers 3-6 and the sheet guide member 16, the sheet can be folded 
zig-zag. The reciprocating movement of the sheet guide 16 and reversal of 
the direction of rotation of the folding rollers 3-6 can be controlled in 
the manner explained in UK Patent 1 394 480. 
The feed path for supplying sheets for folding to the folding station 1 
comprises a short horizontal entry table 2, on which a sheet for folding 
can be placed by hand against a side stop 15, which is coincident with a 
side margin of the feed path, and can be pushed along side stop 15 in the 
direction of the folding station, and a second part formed by the 
vertically extending path portion, in which the transport nip 13 is 
located. Between the two parts, i.e. the entry table 2 and the path 
portion, a rather sharp bend 19 is formed in the feed path. 
A transport nip 20 is provided at the end of the entry table 2 which 
transport nip is formed by a disc roller 21 with balls 22 pressing on each 
disc. The light ball pressure allows a manually fed sheet to be laterally 
displaced in the transport nip 20 to enable the sheet to be fed straight 
along the side stop 15. 
The transport roller 11 forming the transport nip 13 is constructed in the 
form of a roller extending over the width of the feed path and somewhat 
thicker at the ends than in the center. This concave roller 11 co-operates 
with a number of loose biasing rollers 12, each pressed by a leaf spring 
against the concave roller 11 to form a transport nip 13 extending 
transverse to the direction of the feed. In the half of the feed path 
where the side stop 15 is located, the distance between adjacent biasing 
rollers 12 is less than in the other half of the feed path, in order to 
exert a greater transport force on a fed sheet on the side-stop side. The 
larger diameter of the concave roller 11 at the side-stop side causes a 
torque to be exerted on a supplied sheet, such torque pulling and holding 
the sheet against the side stop 15. The transport nip 20 formed by balls 
22 permits rotation of the sheet in the nip 20. Thus, if a sheet is fed 
obliquely in the direction of the side stop 15 it is straightened. The 
width of the feed path in the curve 19 permits rotation of the sheet 
produced by the transport nip 13, such rotation being required to pull an 
oblique sheet against the side stop. The curve 19 also ensures adequate 
stiffness of the sheet in a direction transverse to the direction of sheet 
feed in order to prevent the formation of creases in the feed direction. 
In the absence of bend 19, such creases could form by an opposite torque 
being exerted on part of a sheet situated on the half of the feed path 
remote from the side stop 15. The opposite torques exerted by the concave 
roller on a wide sheet which is situated on both halves of the feed path 
ensure that the sheet is straightened in a zone past the transport nip 13 
in order to present the sheet straight to the folding station 1 and, 
similarly, is contracted in a zone in front of the transport nip 13. The 
latter is counteracted by the bend 19 just before the transport nip. 
Instead of a concave construction of the roller 11, which is made of 
Desmophan, good results have also been obtained with a straight roller 11 
with a tungsten carbide surface which, by the application of 
pre-stressing, is bent somewhat to achieve the required straightening of 
the sheet. 
Coupled to the driven transport roller 11 is a pulse disc 23 which, on each 
displacement of the peripheral surface of roller 11 over 1 mm, delivers a 
pulse via pulse sensor 24. The diameter of roller 11 is for this purpose 
regarded as a constant. In order to ensure that the leading edge of a 
sheet in the folding station enters the folding rollers 3 and 4 straight, 
the folding rollers are released from one another for the passage of the 
leading edge and, after the passage of the leading edge, are again pressed 
on one another to form a transport and folding nip 8. To free the nip 8, 
one end of the folding roller 3, situated on the side-stop side, is lifted 
by a lifting magnet intended for the purpose, while the other end of the 
folding roller 3 remains pressed on folding roller 4 in order to continue 
rotating with the driven folding roller 4 during the release of the nip 8. 
To discharge a sheet from the folding station 1 after it has been folded 
the required number of times, a discharge deflector 25 is introduced into 
the folding path after the last fold so that the folded sheet is deflected 
downwards on its next movement in the direction of folding rollers 3, 4 
and deposited in a collecting tray 26. On the side-stop side, the tray 26 
is provided with a part 27 which, as considered in the direction of 
discharge, is longer than the rest of the tray 26 for collecting a sheet 
folded in two directions, such sheet being longer in the discharge 
direction than a sheet folded in one direction. 
For the zig-zag folding of 1 m wide sheets, the transport rollers 11, 12, 
the folding rollers 3-6 and the sheet-guide member 16 must at least have 
the same length. For adequate rigidity at that length, the rollers and 
guide member must have dimensions such that the distance A between the 
folding nips 8 and 9 is approximately 90 mm minimum. The distance B 
between the transport nip 13 and each of the folding nips 8 and 9 must 
also be about 90 mm minimum, as considered along the shortest path that a 
sheet can follow therebetween. For the maximum compactness of construction 
of the folding device, the folding device shown in FIGS. 1 and 2 is so 
constructed that A=B=90 mm. 
The description given hereinbefore is considered sufficient for an 
understanding of the mechanical action of a folding device according to 
the present invention. 
The description which now follows relates to the elements required to 
control the folding device according to the invention. The control system 
of the folding device shown in FIGS. 1 and 2 comprises three detectors 30, 
31, and 32 disposed at the feed path for a sheet to be folded, these 
detectors delivering detection signals to a control device 33 in response 
to the detection of the leading and trailing edges respectively of a 
supplied sheet, such detection signals being delivered so that operative 
parts of the folding device can be activated at the required times, e.g. 
driving transport rollers 12 and 11 in the feed path, lifting of folding 
roller 3 during the entry of the leading sheet edge, driving the folding 
rollers 4 and 6 in one of two opposite directions, and activation of the 
discharge deflector 25 to discharge the folded sheet. 
Detector 30 comprises a photo-sensitive element 35 disposed beneath a 
diaphragm aperture 36 formed in the entry table 2 at a short distance C 
from the side stop 15 and at a distance D from detector 31 which, as 
considered in the direction of sheet feed, is disposed just after the 
transport nip 13. In the stand-by position of the folding device, the 
photo-sensitive element 35 is illuminated by a point light source 37, e.g. 
an LED, disposed straight above the diaphragm aperture 36 and the 
photosensitive element 35, the point light source 37 being disposed in a 
cap 38 secured to the side stop 15. The distance between cap 38 and the 
entry table 2 is sufficient to allow unobstructed supply therebetween of a 
sheet already folded in one direction. The cap 38, diaphragm aperture 36 
and the distance therebetween have dimensions such that the presence or 
absence of ambient light does not result in any difference in the response 
of the photosensitive element 35. The use of a detector 30 reacting to 
interruption of a light beam by a passing sheet has the advantage that the 
detector 30 is not sensitive to transparent sheets. Since transparent 
sheets are always original drawings, this prevents their being mistakenly 
folded. 
A sheet supplied against the side stop 15 over the entry table 2 interrupts 
the light beam between LED 37 and photosensitive element 35, in response 
to which element 35 delivers a first signal 40 at the time that the 
leading sheet edge interrupts the light beam and a second signal 41 at the 
time that the trailing edge passes and again allows the beam of light to 
reach the photosensitive element 35. Signals 40 and 41 are fed to the 
control device 33 which, in response to signal 40, delivers a start signal 
42 to switch on the coupled drive of the transport rollers 21 and 11 and, 
in response to signal 41, delivers a control signal 43 to activate the 
folding station 1 in dependence on the detected length of the supply 
sheet, such detection being explained hereinafter. 
Distance C is approximately 20 mm, small enough to ensure that only a sheet 
supplied along side stop 15 can interrupt the beam of light between LED 37 
and the photosensitive element 35 to activate the folding device and large 
enough to prevent a sheet supplied fairly obliquely along the side stop 15 
from passing with its side edge over the diaphragm aperture 36 and thus 
giving a detection signal at the wrong time, e.g. to detect too short a 
sheet length. The distance D is about 410 mm. The choice of this 
dimension, which governs the length of the entry table 2, is explained 
hereinafter. As described hereinbefore, detector 31 is disposed just after 
the transport nip 13, e.g. at a distance E therefrom which is 20 mm. 
Detector 31 is constructed as a vane detector, a passing sheet edge 
turning the vane to produce a detection signal 46. The distance F from 
detector 31 to a line forming the extension of the side stop 15 is less 
than the minimum width that a sheet folded in one direction can have, 
e.g., in the case of a conventional minimum folding width of a folded 
packet of 190 mm the distance F is 150 mm. Thus, detector 31 is always 
activated by the leading edge of a sheet transported without slip through 
the transport nip 13. The control device 33 in response to the reception 
of an associated detection signal 46, delivers a control signal 47 to 
start the drive for the rollers 3-6, after expiration of a preset period 
in which the control device 33 may have processed a signal from a detector 
32 (to be described hereinafter) for the leading sheet edge or the 
extension thereof, in a direction in which the leading sheet edge is fed 
by sheet guide member 16 between the briefly freed folding nip 8 and a 
folding program set on control panel 49 is performed. Simultaneously with 
the reception of detection signal 46, the control device 33 starts a count 
of pulses delivered by the pulse sensor 24. The control device 33 stops 
this pulse count on reception of a detection signal 41 delivered by 
photosensitive element 35, on passage of the trailing edge of a supplied 
sheet past element 35. Taking into account the fixed distance D between 
the detectors 30 and 31, the control device calculates from the pulse 
count reached the exact length of a supplied sheet, this measurement being 
necessary to determine the dimension of a variable folding length within a 
set folding program for standard sheet formats. For example, for folding 
sheets of the A3, A2, A1, A0 DIN format, or formats which do not differ 
greatly therefrom and which can be folded in accordance with the same 
folding pattern as the associated DIN format, with only a difference in 
the size of the variable folding lengths within that pattern. 
By means of a control panel 49 the control device 33 can be set to a number 
of folding programs for the zig-zag folding of as yet unfolded sheets of 
different formats to form a packet with a standard dimension, e.g. a 
folding program 50 for a packet having a width of 190 mm, a folding 
program 51 for a packet with a width of 210 mm without a binding edge, and 
a folding program 52 for a packet with a width of 210 mm with a binding 
edge, these folding programs giving the folding patterns shown in FIG. 3 
for the sheet formats A3, A2, A1 and A0. 
The folding patterns shown in FIG. 3 in respect of the folding programs 50, 
51 and 52 have a 5 mm projection of the top sheet of the drawing on which 
the drawing legend is disposed, such top sheet being at the bottom of the 
packets shown in the figure. This projection is adjustable between 0 and 5 
mm. The binding edge, which is 20 mm wide in the case of folding program 
52, is also adjustable to 25 and 30 mm. 
The folding patterns shown in FIG. 3 result in a zig-zag folded packet for 
the exact DIN formats whose folds, counting from the leading edge (the 
edge on which the legend is situated) are at the following distances in 
mm: 
______________________________________ 
Folding program 50: 
A3: 185 115 
A2: 182 95 90 107 
A1: 190 185 185 140.5 140.5 
A0: 190 185 180 180 134 134 
Folding program 51: 
A3: 195 105 
A2: 210 192 
A1: 210 205 110.5 
110.5 
A0: 210 205 100 100 184 184 
Folding program 52: 
A3: 190 105 
A2: 190 95 90 97 
A1: 190 185 130.5 
130.5 
A0 190 185 180 180 124 124 
______________________________________ 
In the case of small differences from the sheet lengths which are 
respectively 420, 594, 841 and 1188 mm for the A3, A2, A1 and A0 formats, 
in the case of the folding patterns for A3 and A2 the position of the last 
fold is adapted and, in the case of the folding patterns for A1 and A0, 
the position of the last two folds is adapted so that the trailing sheet 
edge again has the required position in the packet. Variation of the 
position of the last fold or last fold but one is indicated in the folding 
patterns by &lt;&lt; and &gt;&gt; respectively. 
The distance D between the detectors 30 and 31 must be less than the length 
of the smallest standard sheet format for folding, thus in the case of A3 
as the smallest format for folding it must be less than 420 mm, in order 
to enable the exact sheet length to be determined by pulse counting. 
However, the distance D must be large enough to enable the appropriate 
folding pattern of the set folding programs 50, 51 and 52 to be settled in 
good time. It is sufficient for this to take place in good time for the 
standard formats smaller than the largest standard format. In the case of 
non-detection of the smaller standard formats, the control device assumes 
that the largest standard format or a sheet format differing only slightly 
therefrom has been presented. It will readily be seen from the folding 
patterns shown in FIG. 3 that the folding patterns for A1 and A0 of 
folding program 51 are the most critical. The processing of the first 520 
mm thereof is the same. This means that after the supply of 520 mm of an 
A1 format past detector 31, detector 30 must have released the trailing 
edge of the sheet so that the distance between detectors 30 and 31 must be 
greater than 841-520=321 mm in order to enable each required standard 
folding pattern to be set in good time. However, in accordance with a 
different criterion to be described hereinafter, the distance D must be 
389 mm minimum. In the folding device shown in FIGS. 1 and 2, this other 
criterion is taken into account with D=410 mm. 
Detector 32, which like detector 31 is constructed with a vane which can be 
turned by the leading edge of a supplied sheet, is disposed, as considered 
in the direction of sheet feed, at approximately the same level as 
detector 31, but at a distance G from the side stop 15 which is smaller 
than the minimum width of an unfolded sheet fed in the longitudinal 
direction. This width is, for example, the width of an A3 sheet=297 mm or 
the width of the American B format=279 mm. However, the distance G is 
larger than the maximum width of a packet folded in one direction. This 
width is, for example, the width of the A4 format=210 mm or the width of 
the American 7".times.9" format=230 mm. The maximum possible distance G is 
advantageous in order that a side of a packet which has already been 
folded in one direction and is fed obliquely may be prevented from 
activating detector 32 and thus unintentionally switching the folding 
device to a folding program for making a first fold. In order to prevent 
the detector 32 from detecting no leading edge in the case of detection of 
the leading edge by detector 31 in the event of an unfolded sheet whose 
leading edge extends obliquely rearwardly from the side stop 15, e.g. in 
the event of a nick in the leading edge at the location of detector 32, 
with the result that the packet is detected incorrectly as being one 
already folded in one direction, the control device 33 does not process a 
detection signal 48 delivered by detector 32, until the leading edge of a 
sheet is a predetermined number of counting pulses past detector 31. This 
number, for example, corresponds to a distance of 10 mm sheet movement. 
Only at that time is the drive for the folding rollers 3-6 started so that 
if a folding program has been set for folding a packet already folded in 
one direction the folding rollers can be driven faster than if a folding 
program has been set to fold a sheet in the first direction, in accordance 
with Netherlands patent application 9301483 in the name of Oce-Nederland 
B.V. 
On detection of the leading sheet edge by both detector 31 and detector 32, 
a folding program set on the control panel 49 is activated with the 
folding pattern associated with the zone length detected by detectors 30 
and 31 and after detection thereafter of the trailing sheet edge by 
detector 30 the position of the last and the last two folds, respectively, 
is detected in accordance with the exact sheet length detected, and 
performed accordingly. Given a distance between detector 31 and each of 
the folding nips 8 and 9 of 90-2=88 mm and a corresponding sheet movement 
between the time that a folding command is given and the fold is actually 
made, the folding command for making the next-to-last fold in an A0 sheet 
must not be given later than the time that the future folding line will be 
situated at detector 31. Since at that time the trailing edge may still be 
at detector 30, the distance D in the case of folding program 51 must be 
greater than 205+184=389 mm. In the case of sheets having a length 
considerably different from the standard lengths, the pattern for a 
standard folding with a variable intermediate fold cannot be determined 
until the exact sheet length is known. For this purpose, the detector 30 
must be at a considerable distance from folding station 1, and this would 
require a long entry table. In order that such sheets can nevertheless be 
folded to standard packet dimensions without the need for a long entry 
table, a folding program can be set on control panel 49 for sheets in 
cases where it is not known whether they have a length within 
predetermined length zones around standard lengths. In accordance with 
that folding program, the last fold instead of the next-to-last fold is 
located at a variable position for greater sheet lengths (A1 and A0). 
Since, for this, the exact length dimension must be known at a later time, 
it is sufficient to use the short entry table too. 
If, after expiration of a short period after activation of detector 31, in 
which period there is a 10 mm sheet movement, detector 32 has not been 
activated, then the control device 33 sets the folding station 1 to a 
folding program for folding the supplied sheet at predetermined regular 
distances. Thus, a sheet already folded in one direction will be folded 
once or twice depending upon the length of the packet. The first fold is 
always made at 297 mm. If the sheet is shorter than 297+297+110 mm, the 
second fold is made at a distance from the first fold such that the 
distance between the second fold and the trailing edge is 110 mm. If the 
sheet is longer than 297+297+110 mm, the second fold is made a distance of 
297 from the first fold. The operation of the folding device described 
hereinbefore is explained in the flow diagram given in FIGS. 4A, 4B and 
4C. 
The present invention being thus described, it will be obvious that the 
same may be varied in many ways. Such variations are not to be regarded as 
a departure from the spirit and scope of the invention, and all such 
modifications as would be obvious to one skilled in the art are intended 
to be included within the scope of the following claims.