Apparatus for folding in the bottom of a cardboard pack

A description is given of an apparatus for folding in the front face of a pack (1, 1') made of cardboard coated with plastics material, the front face of which pack is quadrangular in the plan view in the folded in condition and has a transverse sealing seam (5) which can be folded over, having a fold member (b) and a companion fold member (a), which are both driven movably along specific paths of movement by at least one lever mechanism (8-13), and amongst which a conveyer is arranged at a spacing away in the Y-extent, which conveyer moves the packs (1, 1') in the X-extent, wherein the Y-axis is vertical to the X-axis and the zero point of the axes (X, Y) is disposed in the end fold position of the two fold members (a, b) so that the bottom of a pack can be folded in one single step without any subdivision into pre-folding and re-folding steps, and so that no component parts of the machine engage in the pack, preferably not even over the open pack, it is provided that a Y-Z-plane extending in the Z-extent is disposed in the Y-axis and is intersected vertically by the X-axis, that the paths of movement of both fold members (a, b) extend symmetrically to each other relative to the Y-Z-plane, wherein the paths of movement in the X-Y-plane is described as a superposing of a translatory movement and a rotational movement of the respective fold member, that each fold member (a,b) is secured to a connecting lever (12) which is driven in a controlled manner, that arranged symmetrically to the zero point of the two axes (X, Y) is a centering device for the pack, and that the space for the folding in device is free of structural components above the centering device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an apparatus for folding in a front face of a pack 
made of cardboard material coated with plastics material, the front face 
of which pack when folded in is substantially quadrangular in the plan 
view and has a transverse sealing seam which can be folded over, having a 
fold member and a companion fold member which are both driven movably 
along specific paths of movement by means of at least one lever mechanism 
and amongst which a conveyer is arranged at a spacing away in the 
Y-extent, which conveyer moves the packs in the X-extent, wherein the 
Y-axis is vertical to the X-axis and the zero point of the axes is 
disposed in the end fold position of the two fold members. 
2. Description of the Related Art 
As known, packs made of coated cardboard have a substantially tubular main 
body with front faces at the ends. Usually, the one front face is the lid 
and the other front face is the bottom. At least one of the two front 
faces, e.g. the bottom, is substantially quadrangular in the plan view in 
the folded in condition of known packs. With other packs, the lid is 
provided with a so-called gable type closure which is also quadrangular in 
the plan view. It is also possible to fold over the gable closure so that 
it is flat and so that this front face on the lid side is vertical to the 
tube walls. With this invention whether the front face is a lid or a 
bottom is immaterial. 
A folding in apparatus is also known similar to the kind mentioned in the 
introduction, wherein the front face is a lid. The web of material of the 
pack which is to be closed is circular, and there are various fold- and 
weld stations along the circular web. Each fold station has a fold member 
and a companion fold member which both travel about axes on part circular 
paths, these axes being disposed approximately in the radial extent 
relative to the revolving assembly. It has been shown that the Front walls 
which have to be folded must be pre-folded first of all, because otherwise 
the folding in along the circular paths does not fold the front face 
accurately. The known folding in device thus only produces re-folding, and 
the gable surfaces are also pressed inwardly and are folded inwardly. 
The known apparatus is complicated, expensive and prone to malfunctions due 
to the design of the revolving body and due to the plurality of fold 
stations. 
In addition, the filled and upwardly open packs travel beneath a number of 
movable parts with the known machine, particularly in the fold station, so 
that foreign bodies from overlying structural components are able to fall 
into the open pack. This causes cleaning- and hygiene-related problems. 
SUMMARY OF THE INVENTION 
The aim of the invention therefore is to create a folding in apparatus of 
the kind mentioned in the introduction wherein the front faces, e.g. the 
bottom of a pack, can be folded in in one single step without any division 
into a pre-folding operation and a subsequent re-folding operation. During 
the folding operation, none of the parts should engage in the pack, 
preferably not even structural components over the open pack, and shortly 
afterwards sealing should be effected in the fold position. 
This problem is solved according to the invention in that a Y-Z plane 
extending in the Z-extent is disposed in the Y-axis and is intersected 
vertically by the X-axis, that the paths of movement of both fold members 
extend symmetrically to each other relative to the Y-Z-plane, wherein the 
paths of movement in the X-Y-plane are described as the superposing of a 
translatory movement and a rotational movement made by the respective fold 
members, that each fold member is fixed to at least one connecting lever 
which is driven in controlled fashion, that arranged symmetrically to the 
zero point of the two axes is a centering device for the pack, and that 
the space for the folding in device is free of structural components over 
the centering device. 
The entire folding in apparatus according to the invention can preferably 
be used for folding in the bottom of a pack, and for this reason the 
description is firmly related to a bottom, but the lids can also be 
designed in this way. A bottom of this kind is substantially quadrangular 
in design in the plan view in the folded in condition, and may even be 
flat. In the case of a bottom, this is important so that the pack has a 
good basis. 
The series of filled packs which have the open bottoms upwards is guided at 
least in the fold region of the apparatus according to the invention a 
little way onto a straight belt in the X-extent. Expediently, the X-extent 
is horizontal. A Z-extent can be imagined as extending vertically thereto 
which is also disposed horizontally. A Y-axis can also be imagined for the 
spatial ratio which is vertical to the other two axes. According to the 
invention, a zero point is defined where the three axes intersect and 
where a Y-Z plane is supposed as existing which is intersected vertically 
by the X-axis. The first teaching of the invention in solving the 
afore-mentioned problem is that the paths of movement of both fold members 
should extend symmetrically to each other relative to the Y-Z-plane. The 
zero point therein is the end point where the two fold members touch when 
folding in of the bottom is complete, with the end of the paths of 
movement also being disposed at that place. 
The start of the paths of movement is also above and outside the two sides 
at a spacing from the Y-Z-plane, since the starting-, zero- or rest 
positions are disposed there both for the fold member and for the 
companion fold member. 
If a vertical plane is imagined as being disposed centrally through the 
pack in a vertical direction to its direction of conveyance in the X-axis, 
then the central plane of the open pack must be disposed in the Y-Z-plane 
at the latest at the moment when the frontmost edges of the fold member 
and companion fold member just start to touch the bottom which is not yet 
folded in. 
Each path of movement of the fold members represents a superposing of a 
translatory movement and a rotational movement of each of the fold 
members, i.e. the fold members are not rotated about fixed axes, and are 
not even moved simply in a straight line. Instead, it is provided that 
each fold member is fixed to a connecting lever which is controlled and 
driven in a specific way so that they are moved towards the bottom which 
is still open and which has to be folded in, and folded in accurately 
without any pre-folding. 
It has been shown that even when the fold members have very accurate paths 
of movement, the bottom cannot be folded along the junction fold lines, 
only along these lines which are disposed at the tube end of the pack and 
which represent the boundary at the front face fold region, so to say. 
Often, undesirable buckled folds have been noted which also extend beneath 
the junction fold line into one or more tube walls. 
Therefore, according to the invention, it is also provided that a centering 
device be disposed symmetrically to the zero point, into which apparatus 
the pack is introduced and supported during the folding operation. 
By virtue of the afore-mentioned features according to the invention, the 
front wall in question is folded in correctly, whether this front wall be 
the bottom or the lid, without the front face fold members having to be 
pre-folded. Furthermore, the gable surfaces are folded out in the 
Z-extent. The corner points of the afore-mentioned junction fold line are 
not disposed on a circle, and due to the combination of translatory and 
rotational movement the fold members according to the invention inevitably 
cause the bottom of the pack which has not been prefolded to be folded in 
the desired and correct way. Hygiene-related problems are considerably 
improved since none of the structural parts are disposed in the spatial 
area of the folding in device over the centering device, and thus over the 
pack which is still open. Despite the fact that only one single step is 
needed for the pre-folding operation to produce correct folding of the 
front wall, none of the parts of the machine engage into the pack. Since 
only one fold member and one companion fold member are provided which 
prepare the folding operation whereupon a sonotrode can be used, for 
example, to weld the transverse sealing seam, not only are the risks from 
foreign bodies reduced, but the apparatus also has fewer parts and thus 
operates more reliably. 
The connecting levers driven in controlled manner represent the components 
of a link rod system which accurately monitors and determines the sequence 
of movement made by the components spatially over the passage of time. 
It is particularly preferable according to the invention if each path of 
movement in the initial region extends at an angle of less than 
45.degree., preferably less than 30.degree., relative to the X-axis, and 
extends in the end region at an angle of more than 45.degree., preferably 
more than 60.degree. relative to the X-axis. The initial region is thus 
disposed at the maximum distance away from the zero point, and here the 
fold members move flatter than in the end region where they move more 
steeply into a position towards the end fold position with the bottom 
parts of the packs which are to be folded. 
Therein, according to the invention, it is particularly advantageous if 
each path of movement, has a continuous transition between the initial 
region and end region. Folding can be done properly and accurately, if two 
straight paths are not adjacently disposed making a transition into each 
other by way of a buckled point, but if the path of movement is steady and 
thus has a gradually changing inclination, with each path of movement 
being rounded, so to speak. 
More accurate investigation has led to the result according to the 
invention such that the problem is solved particularly well and correctly 
if the path of movement of the fold member in the first quadrant in which 
the x-values on the X-axis and also the y-values on the Y-axis are 
positive extends in a specific region of flatness which is defined by two 
curves. Here, in the first quadrant, by way of example, the lower boundary 
curve is called y.sub.1 =f.sub.1 (x), and the upper boundary curve is 
called y.sub.2 =f.sub.2 (x) with 
EQU f.sub.1 (x)=a.sub.1 +b.sub.1 x-c.sub.1 x.sup.2 +d.sub.1 x.sup.3 -e.sub.1 
x.sup.4 +g.sub.1 x.sup.5 
and 
EQU f.sub.2 (x)=a.sub.2 +b.sub.2 x-c.sub.2 x.sup.2 +d.sub.2 x.sup.3 -e.sub.2 
x.sup.4 +g.sub.2 x.sup.5 
In the second quadrant, for positive y-values in the Y-extent and negative 
x-values in the left negative extent of the X-axis, the path of movement 
should extend in a region of flatness which is also defined by two other 
curves which are called 
EQU f.sub.3 (x)=a.sub.1 +b.sub.1 x-c.sub.1 x.sup.2 +d.sub.1 x.sup.3 -e.sub.1 
x.sup.4 +g.sub.1 x.sup.5 
EQU f.sub.4 (x)=a.sub.2 +b.sub.2 x-c.sub.2 x.sup.2 +d.sub.2 x.sup.3 -e.sub.2 
x.sup.4 +g.sub.2 x.sup.5 
wherein 
a.sub.1 =-135,006 
b.sub.1 =+23,452 
c.sub.1 =+1,398 
d.sub.1 =+0,041922 
e.sub.1 =+6,183.times.10.sup.-4 
g.sub.1 =+3,571.times.10.sup.-6 
a.sub.2 =+17,312 
b.sub.2 =+2,002 
c.sub.2 =+0,213 
d.sub.2 =+1,355.times.10.sup.-2 
e.sub.2 =+4,022.times.10.sup.-4 
g.sub.2 =+4,386.times.10.sup.-6. 
It has been found that folding cannot be done completely if the front edges 
of the fold member and of the companion fold member do not extend in the 
aforementioned surfaces. 
However, on the other hand, the folding in operation is particularly 
favourable if the path of movement of the frontmost edge of the respective 
fold member which comes into engagement with the fold lines of the bottom 
wall which is to be folded in follows a specific curve definition, i.e. a 
specific path of movement f.sub.a (x) in the first quadrant and f.sub.b 
(x) in the second quadrant. Both curves are composed computationally of 
two partial curves, namely, for the first quadrant, a curve y.sub.a6 
=f.sub.a6 (x) from the domain of definition D.sub.1 ; and a second partial 
curve y.sub.a7 =f.sub.a7 (x) for the domain of definition D.sub.2, which 
curve extends towards the region of initial movement. Therein, according 
to the invention: 
EQU f.sub.a6 (x)=-a.sub.3 +b.sub.3 x-c.sub.3 x.sup.2 +d.sub.3 x.sup.3 -e.sub.3 
x.sup.4 
for D.sub.1 {x/0.ltoreq.x.ltoreq.6}, and 
EQU f.sub.a7 (x)=a.sub.4 +b.sub.4 x-c.sub.4 x.sup.2 +d.sub.4 x.sup.3 -e.sub.4 
x.sup.4 
for D.sub.2 {x/6.ltoreq.x.ltoreq.40}. 
For the second quadrant, thus for positive y-values and negative x-values, 
the path of movement is correspondingly composed of the curve y.sub.a8 
=f.sub.a8 (x) (in the end region) and y.sub.a9 =f.sub.a9 (x) (in the 
initial region). Therein: 
EQU f.sub.a8 (x)=-a.sub.3 -b.sub.3 x-c.sub.3 x.sup.2 -d.sub.3 x.sup.3 -e.sub.3 
x.sup.4 
for D.sub.3 {x/-6.ltoreq.x.ltoreq.-0}, and 
EQU f.sub.a9 (x)=a.sub.4 -b.sub.4 x-c.sub.4 x.sup.2 -d.sub.4 x.sup.3 -e.sub.4 
x.sup.4 
for D.sub.4 {x/-40.ltoreq.x.ltoreq.-6}, wherein 
a.sub.3 =8,7013 
b.sub.3 =14,224 
c.sub.3 =3,4512 
d.sub.3 =0,40883 
e.sub.3 =0,017696 
a.sub.4 =10,216 
b.sub.4 =1,5685 
c.sub.4 =0,046046 
d.sub.4 =0,68195.times.10.sup.-3 
e.sub.4 =0,39415.times.10.sup.-5. 
For the regional values D.sub.1 to D.sub.4 it can be supposed that for x 
the millimetre values of a pack for liquids can be used. For example, the 
width of the bottom of a pack in the plan view, viewed in the Z-extent, is 
70 mm. 
Therefore, it is expedient if according to the invention it is provided 
that the length of each path of movement in the X-extent is somewhat 
greater than, or equal to, half the length of the bottom in the X-extent. 
Also, according to the invention it is provided that the centering device 
has two parallel centering bars which are at a spacing apart and which 
extend in the direction of conveyance of the pack, wherein the spacing 
between them is measured in the Z-extent. These two elongate centering 
bars have sharp edges over which the afore-mentioned lower junction fold 
lines are disposed beneath the parts of the gable wall regions which are 
to be folded outwardly, so that the junction fold line disposed on the 
gable surface is buckled with the aid of the respective centering bar, and 
it is ensured that the upper peak of the gable moves outwardly in the 
Z-extent. 
This means that advantageously in the sides which are transverse to the 
longitudinal extent of the centering bars, i.e. in the side walls which 
are parallel to the Y-Z-axis, the tension is increased, so that when 
folding takes place along the end fold line, a neater inward fold of the 
bottom closure is produced. The centering bar ensures that during the 
folding together operation, the gable walls are actually folded outwardly 
in the Z-extent. Without these centering bars, falling or folding to the 
inside could happen. Therefore, the centering device advantageously 
provides for secure and proper folding, even if the impressions made in 
the end face region of the pack, e.g. the impression made in the bottom 
region, is somewhat weaker than is ideal. A weaker impression means that 
costs can be cut. 
Therein, it has been shown to be particularly advantageous if according to 
the invention the ratio of the spacing between the centering bars and the 
width of the pack in the Z-extent transversely to its direction of 
conveyance is 095. This produces the neatest folding and the best increase 
in tension in the tube walls which ape not supported by abutment members. 
The apparatus according to the invention is also characterised in that the 
connecting lever of the companion fold member is connected at a first 
point of rotation to one end of an output fold guide rod which is mounted 
at the opposite end at a stationary point of rotation and is connected to 
a drive cam at a second point of rotation, the drive cam being secured to 
a toothed drive wheel which is in meshing engagement with the toothed 
drive wheel of the other connecting lever such that the Y-Z-plane is 
vertical to the connecting line of the points of rotation of the toothed 
wheel. Thus it is possible to move both the fold member and also the 
companion fold member synchronously to each other on the desired paths, 
and to keep the lever outside the region above the path of movement of the 
open packs, preferably arranged in outwardly displaced fashion in the +Z 
or -Z-extent. 
It is also expedient according to the invention if the fold member extends 
at the front so that it tapers in its cross-section into the shape of a 
panel, and if the companion fold member is in the form of an anvil against 
which a sonotrode can be pushed in a path of movement which is preferably 
different in time and/or place from the path of movement of the fold 
member. With reference to the paths of movement and functions, it has 
already been stated that the actively folding edges of the companion fold 
member, on the one hand, and of the fold member, on the other hand, should 
move in the domains of definition, and therefore it is expedient if the 
fold member is designed in such a way that it tapers at the front into a 
panel which has a straight blade-fine pressure- and fold edge. A fold 
member of this kind could also be referred to as a folding metal sheet, 
and it fulfills its function completely and allows space for a sonotrode 
to be introduced which also rests on the companion fold member and can be 
used for welding purposes, since the companion fold member is in the form 
of an anvil. The anvil is a clean structural unit which is completely 
smooth on the outside, so that the upwardly open pack can even move 
beneath the anvil, without the afore-mentioned problems of foreign bodies 
occurring. The anvil and the like are thus placed outside the path of 
movement of the open packs. 
Further advantages, features and possible applications of the present 
invention will emerge from the following description of a preferred 
embodiment, in conjunction with the drawings, wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
Three packs 1 or 1' are disposed above a conveyor belt, not shown, which 
moves horizontally in the positive extent X, wherein the pack 1' is 
already ready and folded and is provided with a welded transverse sealing 
seam. With the embodiment shown here, the lid of the pack is provided at 
the bottom, and the pack is filled through the bottom, and the front face 
walls are thus the bottom walls which are separated from the tube side 
walls by the junction fold line 2. The junction fold line 2 extends in the 
X-extent, whilst in FIG. 5 the junction fold line 2' extends in the 
Z-extent. The Z-extent is vertical to the plane of the paper in FIGS. 1 to 
4 and 7, 7a. 
The triangular gable faces are denoted by the reference numeral 3 and at 
the top, on the outside, they have a peak 4 which is disposed opposite the 
junction fold line 2 and which is supposed to be folded out in the 
Z-extent or -Z-extent (FIG. 5). The pack 1' is in a condition where the 
folding operation has been completed, so that the peak 4 of the gable can 
be seen directly beneath the transverse sealing seam 5. The longitudinal 
sealing seam of the pack is denoted by the reference numeral 6 in FIG. 5. 
So that the front face 2-4 of the pack 1 can be folded in, the folding 
metal sheet b and the anvil a are moved by means of a lever mechanism 
denoted generally by the reference numeral 6 in such a way that the fold 
edges 7 of the folding metal sheet b and 7' of the anvil a move on 
predetermined curved paths. In FIG. 1, the folding metal sheet b and the 
anvil a are in the withdrawn position of rest, whence the fold edges 7, 7' 
can enter the initial region of the folding operation which is disposed in 
FIGS. 7 and 7a at a spacing from the zero point 0 at the outer end of the 
curves disclosed there. 
For synchronous movement of the lever mechanism 6, a toothed drive wheel 8 
and a toothed output wheel 9 in meshing engagement therewith are provided. 
A drive cam 10 which is fixedly connected to the toothed drive wheel 8 is 
pivotable about the stationary point of rotation I in such a way that at 
the outer end the drive cam 10 with point of rotation II can be moved on a 
circle to which the connecting lever 11 on the side of the anvil is 
hinged. This connecting lever is also hinged to the movable point of 
Potation III of a fold guide rod 12 on the anvil side, this fold guide rod 
being pivotable about the stationary point of rotation IV. This therefore 
promotes movement both of the support means 13 which is arranged fixedly 
on the connecting lever 11 and also of the anvil a which is held by the 
support means. 
Disposed on the side of the folding metal sheet are similar components 
which are pivotable about the stationary axis of rotation I', the movable 
axis of rotation II', the movable axis of rotation III', the stationary 
point of rotation IV'and the stationary point of rotation V'. 
Whilst the axes of Potation (points of rotation) of the components are best 
seen in FIG. 1, the components on the side of the folding metal sheet will 
now be described with the aid of FIG. 2. 
An output cam 14 is fixedly connected to the toothed output wheel 9, the 
output cam driving the connecting lever 15, here on the side of the 
folding metal sheet, in the same way as on the anvil side, to the bottom 
end of which connecting lever the folding metal sheet b is secured. Here 
too a fold guide rod 18 is hinged at the movable point of rotation III', 
and is able to pivot about the stationary point of rotation IV'. 
Independently of the movement of the output cam 14, a guide lever 17 is 
able to rotate about the point of rotation I' to which the sonotrode unit, 
generally denoted by the letter S, is hinged. The converter housing 19 of 
this latter is hinged parallel to the guide lever 17 for the sonotrode 
unit to a drive lever 20 which is also shown in FIG. 1 with its stationary 
point of rotation V. 
The guide lever 17 for the sonotrode unit S and the drive lever 20 arranged 
parallel thereto can thus be moved separately by the output cam 14, moving 
in parallelogram fashion, the levers 20 and 17 being equal in length. It 
can thus be seen that the sonotrode unit S together with the sonotrode 21 
can move and is driven separately by the folding metal sheet b. 
FIG. 2 shows the central pack 1" in an intermediate fold condition, wherein 
the front edges 7 and 7' of the folding metal sheet b and of the anvil a 
have already performed up to more than one half of the folding operation. 
For this reason, the peak 4 of the gable has already moved downwardly on 
the pack longitudinal central line 22' in comparison with the central line 
22 of the pack 1. It will be appreciated that the longitudinal central 
line 22 of the pack moves with the pack. The central line 22' is disposed 
in the Y-Z-plane which goes through the zero point, as can be seen in FIG. 
7. This central line 22' is also disposed in the Y-Z-plane which goes 
through the zero point, which plane is intersected vertically by the 
connecting line 23 between the points of rotation I, I' of the toothed 
wheel. 
In the state shown in FIG. 3, the folding operation has been brought to a 
close, and the support means 13 for the anvil a is placed on the 
stationary abutment 24, so that weld pressure can be properly and 
accurately resisted without any load from the connecting lever 11 and its 
mountings, this weld pressure being applied by the sonotrode 21 which can 
move away over the flat folding metal sheet b and can clamp and weld the 
transverse sealing seam 5. 
The two centering bars 25 are disposed in the region of the Y-Z-plane which 
passes through the zero point, but they are not shown in FIGS. 1 to 3 for 
the sake of simplicity. They are described with the aid of FIGS. 4 to 6. 
The elongate centering bars 25 which are viewed from the side and from 
above in FIGS. 4 and 6 respectively extend in the X-extent in which a view 
is taken in FIG. 5 from the first into the second quadrant, thus in the 
X-extent. 
The upper edge of the two centering bars 25 is arranged between 1 and 5 mm, 
preferably between 1.5 and 3 mm, beneath the junction fold line 2 between 
the tube of the pack, shown broken off at the bottom, and between the 
upper front face region 2, 4, 6. Also, the two centering bars 25 in FIG. 6 
are at a specific spacing apart A, 67 mm for example, in one embodiment 
wherein the width B of the pack is 70 mm. Thus, the ratio V of the spacing 
A to the width B of the pack is 0.95. This means that when the pack 1 is 
introduced between the two centering bars 25 in the extent +X it is 
slightly compressed so that the actual width B of the pack between the 
centering bars is then likewise only 67 mm. The resultant advantageous 
increase in tension in the region of the junction fold line 2' (FIG. 5) 
have already been mentioned. 
After the folding operation has been completed, the pack 1' leaves the 
centering bars 25. 
FIG. 7 is a diagram of the X-Y-axes with the various curves which result 
for the paths of movement. The region of the third and fourth quadrants 
for all values y&lt;0 is not of interest, and can therefore be disregarded in 
the description hereinafter, and this region is omitted and not shown in 
FIG. 7a. 
FIG. 7 shows the zero point 0 at the point of intersection of the X and Y 
axes between the values -40 and +40 on the X-scale. By way of example, it 
is possible to imagine the numerical values as millimetres. The paper 
plane is set by the X- and Y-axis, and the Z-axis is vertical to the paper 
plane. Its origin is also the zero point 0. The zero point represents the 
end fold position where the front edges 7 and 7' of the folding metal 
sheet b and of the anvil a have reached the position in FIG. 3, the 
transverse sealing seam 5 thus being ready and folded. Therefore, this is 
the end region. The optimum paths of movement are shown by the curves 
f.sub.a (x) and f.sub.b (x) in FIG. 7. If these curves are followed from 
the zero point in an outwardly direction, their intermediate positions are 
passed through, as shown in FIG. 2, for example, for the folding metal 
sheet b and the anvil a. Still further to the outside, i.e. at a spacing 
from the Y- and X-axis, the broken line is reached in the starting region 
of the folding operation, which, with the drawing of the folding metal 
sheet b and the anvil a in FIG. 1 has already been passed since the front 
edges 7 and 7' are disposed there in a position of rest wherein they are 
not even in engagement with the pack. The pack therefore has not even 
moved to the correct position which is only reached by the pack in FIGS. 2 
and 3. 
The ideal paths of movement f.sub.a (x) and f.sub.b (x), i.e. the paths of 
the front edge 7 of the folding metal sheet b (f.sub.a (x) and in the 
second quadrant of the front edge 7' of the anvil a (path f.sub.b (X)) are 
marked by broken lines by curves which move in FIG. 1 in a region of 
flatness. The region of flatness for the folding metal sheet b and thus 
the path of movement f.sub.a (x) is defined by the curves y.sub.1 =f.sub.1 
(x) at the bottom and y.sub.2 =f.sub.2 (x) at the top, all in the first 
quadrant. 
The path of movement f.sub.b (x) for the anvil extends in the second 
quadrant in a region of flatness which is defined by the curves y.sub.3 
=f.sub.3 (x) and y.sub.4 =f.sub.4 (x). 
Expressed in concrete numerical values, the defining curves are as follows: 
EQU y.sub.1 =f.sub.1 (x)=-135,066+23,452x-1,398x.sup.2 +0.041922x.sup.3 -6,183 
. 10.sup.-4 x.sup.4 +3,571. 10.sup.-6 x.sup.5 
EQU y.sub.2 =f.sub.2 (x)=17,312-2,002x-0,213x.sup.2 +1,355 . 10.sup.-2 x.sup.3 
-4,022. 10.sup.-4 x.sup.4 +4,386 . 10.sup.-6 x.sup.5 
EQU y.sub.3 =f.sub.3 (x)=-135,066-23,452x-1,398x.sup.2 -0,041922x.sup.3 -6,183. 
10.sup.-4 x.sup.4 -3,571 . 10.sup.-6 x.sup.5 
EQU y.sub.4 =f.sub.4 (x)=17,312-2,002x-0,213x.sup.2 -1,355 . 10.sup.-2 x.sup.3 
-4,022 . 10.sup.-4 x.sup.4 -4,386 . 10.sup.-6 x.sup.5 
FIG. 7a shows two domains of definition D.sub.1 and D.sub.2 for the first 
quadrant for the x-values; and for the second quadrant two mope domains of 
definition for the x-values, namely D.sub.3 and D.sub.4. 
For the first quadrant, this means that the ideal path of movement f.sub.a 
(x) cannot be represented by one single function, but is sub-divided into 
two sections, namely the section disposed closer to the zero point with 
the domain of definition D.sub.1 in the form of the curve f.sub.a6 (x) and 
the section, disposed somewhat further away, for the domain of definition 
D.sub.2 with the curve f.sub.a7 (x). 
The same applies to the second quadrant. There too, the ideal curve f.sub.b 
(x) for the front edge 7' of the anvil a is sub-divided into two partial 
curves, namely that close to the zero point in the domain of definition 
D.sub.3 for the x-values and that which is somewhat further away from the 
Y-axis in the domain of definition D.sub.4 for the function f.sub.a9 (x). 
Expressed concretely as numbers, for the first quadrant: 
EQU f.sub.a6 (x)=-8,7013+14,224x-3,4512x.sup.2 +0,40883x.sup.3 
-0,017696x.sup.4. 
The outer branch of the curve which reaches in as far as the start of the 
fold region is then defined by the following curve: 
EQU f.sub.a7 (x)=10,216+1,5685x-0.046046x.sup.2 +0,68195 . 10.sup.-3 x.sup.3 
-0.39415 . 10.sup.5 x.sup.4. 
For the second quadrant the same is true: 
EQU f.sub.a8 (x)=-8,7013-14,224x-3,4512x.sup.2 -0,40883x.sup.3 -0.017696x.sup.4 
and for the outer branch of the curve: 
EQU f.sub.a9 (x)=10,216-1,5685x-0.046046x.sup.2 -0.68195 . 10.sup.-3 x.sup.3 
-0.39415 . 10.sup.-5 x.sup.4. 
During operation, a pack 1 is conveyed in the direction of the X-axis into 
a position shown in FIG. 1 (the central pack), wherein the folding metal 
sheet b and the anvil a ape still in their outer positions of rest. 
Whilst the pack 1 is being pushed further in the X-extent, so that its 
vertical longitudinal central axis 22' comes to lie in the Y-Z-plane, the 
front edges 7 and 7' of the folding metal sheet b and of the anvil a move 
towards the upper fold edge of the bottom fold regions of the pack 1, 
which passes through the upper apex 4 of the triangle parallel to the 
junction fold line 2. At this moment, the folding operation begins by 
pressing together by the fold members b and a which are to be moved 
together. The point 4 of the tip of the gable of the gable region 3 moves 
downwardly in the Y-Z-axis, whilst the junction fold line 2 is held by the 
centering bars 25 in the way shown in FIGS. 4 to 6. This folding in 
operation is continued until the position in FIG. 2 is reached. However, 
this is only an intermediate position. The point 4 moves further 
downwardly in the Y-Z-plane until the end fold position in FIG. 3 is 
reached. 
In the meantime, the sonotrode 21 has moved on another path of movement by 
virtue of the parallelogram gear system 17, 20 into the position shown in 
FIG. 3, and shortly afterwards the double cardboard strip of the pack at 
the top is clamped between the front edge 21 of the sonotrode and 
companion surface of the anvil a and welded. This produces the transverse 
sealing seam 5. The front edges 7 and 7' of the folding metal sheet b and 
anvil a then move on the curves f.sub.a (x) and f.sub.b (x), and the pack 
1' reaches the position shown to the right in FIG. 1 whence it is conveyed 
further away. 
It is also possible to move two rows of packs simultaneously in the 
direction of the X-axis into the folding in position if two folding metal 
sheets b and two anvils a are arranged behind each other in the Z-extent, 
as shown by the plan view of the apparatus in FIG. 8. In that drawing it 
is possible to see the above-described components and axes accordingly. 
Therein, it will be appreciated that the anvils a are held by support 
shafts 26, 27 and 28. 
The various positions of movement of the fold guide rod 12, of the guide 
lever 17, of the fold guide rod 18, of the connecting levers 11 and 16 
etc. are shown in FIGS. 1 to 3.