Method and machine for automatically gluing a heat shrinkable plastic film onto the bottom of an open box

A method and machine for gluing a heat shrinkable film (9) onto the bottom of a rigid container (1) that is open at its upper part and has a rectangular or square horizontal section remarkable in that the containers are moved on an endless conveyor (2) that extends longitudinally and in that for each new container (1) that arrives, its height (h) and/or its dimension (a) in the transverse direction is measured and that then from the measurement of the height (h) and/or the dimension (a) in the transverse direction of each container, a glue application device (6) and a device (7) for applying the film is adjusted in relation to the corresponding dimensions of each container (1) in such a way as to position these devices as close as possible to the upper edges of the containers and/or to follow the variations in their transverse dimension (a).

FIELD OF THE INVENTION 
This invention relates to a method and a machine for automatically gluing a 
heat shrinkable plastic film onto the bottom of a rigid container, open at 
its upper part and with a rectangular or square horizontal section. 
BACKGROUND OF THE INVENTION 
For the shipping of groups of diverse products corresponding to different 
orders, containers made of cardboard or similar materials are being used 
more and more at the present time, containers such as American boxes or 
American half-boxes, trays, etc . . . onto the bottom of which the central 
part of a section of heat shrinkable plastic film is glued, the end parts 
of which are left free in order to be able to be folded over the products 
grouped together in the container following preparation of an order. After 
placing the group of products in the container, the container is passed 
through a shrinking tunnel and the plastic film then shrinks onto the 
products holding them firmly in place inside the container, which avoids 
having to use additional fixing elements. 
DESCRIPTION OF THE INVENTION 
The aim of this invention is to provide a method and a machine which allows 
the production of order preparation packaging at a high rate, on a serial 
production basis, by automatically adapting itself to variations in the 
height and/or the horizontal section of successive containers. 
SUMMARY OF THE INVENTION 
To this end, this method of automatically gluing a heat shrinkable plastic 
film onto the bottom of a rigid container open at its upper part and with 
a rectangular or square horizontal section, is characterized in that the 
containers are moved, one after the other, on an endless conveyor 
extending longitudinally, and in that for each new container that arrives, 
one measures its height and/or its dimension in the transverse direction, 
that is to say perpendicular to the direction of advancement of the 
containers on the conveyor, and that then from the measurement of the 
height and/or the dimension in the transverse direction of each container, 
the vertical position and/or the transverse extension of a glue 
application device and a device for applying the film is adjusted in 
relation to the corresponding dimensions of each container in such a way 
as to position these devices as close as possible to the upper edge of 
each container and/or to follow the variations in the transverse dimension 
of each container. 
Another object of the invention is a machine for automatically gluing a 
heat shrinkable plastic film onto the bottom of a rigid container open at 
its upper part and with a horizontal or square section, comprising a 
horizontal endless conveyor driven intermittently, a stand-by station 
located at the upstream end part of the conveyor onto which the successive 
containers are placed and, downstream from this stand-by station, a 
station for the application of the film on the upper part of which is 
situated a device for applying a section of thermoplastic film onto the 
bottom of each container, characterized in that it comprises, between the 
stand-by station and the station for the application of the film, a glue 
application device for projecting the glue, from the top, onto the bottom 
of each container, during its longitudinal displacement between these two 
stations, means for placing and keeping the containers in position, on the 
conveyor, in such a way that one of their longitudinal sides is always 
situated in one and the same vertical and longitudinal reference plane, 
means of measuring the height and/or the transverse dimension of each 
container at the stand-by station and means of adjusting the vertical 
position and/or the transverse extension of the glue application device 
and the plastic film application device in relation to the height and/or 
the transverse dimension of each container in such a way that these two 
devices are positioned as close as possible to the upper edge of each 
container, whatever its height and/or to make the transverse extension of 
these two glue and film application devices correspond to the transverse 
dimension of each container.

DETAILED DESCRIPTION OF THE DRAWINGS 
First to be described, making reference to FIGS. 1 to 9, will be the 
different steps in the method of automatic gluing a heat shrinkable 
plastic film onto the bottom of a rigid container 1 open at its upper part 
and with a rectangular or square horizontal section, this method being 
implemented in a machine represented very diagramatically. In FIG. 1, 
several containers 1 are represented having a variable height h and a 
horizontal section having a variable transverse dimension a and a 
longitudinal dimension b. In the description that will follow, the 
expression "longitudinal" is to be understood as referring to the 
longitudinal direction of displacement, from left to right on the drawn 
Figures, of the containers on a horizontal and longitudinal conveyor 2 of 
any suitable type, the expression "transverse" referring to the direction 
perpendicular to the preceding one. To put it another way, each container 
1 is placed, by any suitable means, on the upstream end or left part A of 
the endless conveyor, then at a standstill, that constitutes a stand-by 
station. While the container 1 is at a standstill at the stand-by station 
or before its arrival at this station, its height h and its transverse 
section and more particularly its transverse dimension a are measured. 
This measurement step is represented by block 3 on FIG. 1. The result of 
these measurements is transmitted to a general command apparatus 4 which 
acts on a device 5 controlling the setting of the vertical position and/or 
the transverse extension of a glue application device 6 and a film 
application device. The film application device 7 is situated above the 
downstream end part of the conveyor 2, defining a film application station 
B. The glue application device 6 can be independent of the film 
application device 7 or linked to it. 
During the first step of the method according to this invention, that is to 
say while the container 1 is immobile at the stand-by station A, the 
vertical position of devices 6 and 7 is set automatically from the 
measurements of the height h and/or the transverse dimension a of the 
container 1, in such a way that they are situated as close as possible to 
the upper edge of the container 1, and/or the transverse extension of 
these devices is set in such a way that it corresponds to the transverse 
dimension a of the container. 
Once suitable settings for devices 6 and 7 have been made, one proceeds to 
the second step of the method which consists of projecting the glue onto 
the bottom of the container 1 by means of the device 6 which includes 
gluing nozzles directed downwards. 
The glue application step can be carried out by causing a longitudinal 
displacement of the glue application device 6 above the container 1 held 
immobile on the conveyor 2. According to a variant, the glue application 
can take place, as illustrated in FIG. 2, during the displacement of the 
container 1 from the stand-by station A toward the film application 
station B. In this case, the glue application device 6 has a fixed 
longitudinal position and it can then be linked to the film application 
device 7, being located on the upstream or left side of it in such a way 
as to be able to be displaced vertically conjointly with device 7. 
FIG. 3 illustrates diagramatically, the drawing in the transverse 
direction, by means of a movable grip 8, of the thermoplastic shrinkable 
film 9 which is wound from a lateral roll 11 located at the film 
application station B. The mobile grip 8 with transverse movement is part 
of the film application device 7 as will be described in greater detail 
below. 
FIGS. 4 and 5 represent the container 1 which has arrived at the film 
application station B and is at rest at this station before application of 
the film 9 onto its glued bottom. On these Figures, longitudinal strips of 
glue 12 have been shown, which have been previously projected onto the 
bottom of the container 1, by the glue application device 6. In FIG. 5, it 
can be seen that the film 9 has been drawn across and above the container 
1 and beyond it, over a variable length which depends on its height h 
and/or its transverse dimension a. While the container 1, with its bottom 
glued, is at station B, a new container 1 of identical or different height 
h and/or identical or different transverse dimension a, is positioned at 
the stand-by station A. 
The following step of the method is constituted by the pressing of the film 
9 to the interior of the container 1, in such a way that it is applied 
against the bottom of the container 1, as illustrated in FIGS. 6 and 7. To 
this end, a vertically mobile pressing head 13, which forms part of the 
device 7 for applying the film 9, and which is situated above this film, 
is lowered in such a way that it is introduced into the container and 
applies the film 9 with pressure against the bottom of the container 1, 
for a period of time, of the order of 2 seconds for example, that is 
sufficient to ensure effective bonding. During the final part of the 
pressing, a cutting device 14 is actuated to separate the section of film 
which is stuck to the inside of the container 1 from the supply roll 11. 
After the period of time provided for the pressing has passed, the pressing 
head 13 is moved upwards in such a way that it is clear of the container 
1, as is represented in FIGS. 8 and 9. The container 1, fitted with the 
section of heat shrinkable film 9, the central part of which is glued to 
the bottom of the container 1 and whose end parts are free, can then be 
moved on when the conveyor is set going again. 
A non-limitative embodiment of a machine for implementing the method 
according to this invention will now be described making reference to 
FIGS. 10 to 13. 
In the embodiment represented in FIGS. 10 and 11, the endless conveyor 2 
which causes the successive displacement of the various containers 1, 
comprises a horizontal transfer path 15 the upstream end part of which is 
constituted by horizontal and transverse rollers 16 and the downstream 
part by a smooth plate 17. The various containers 1 are displaced on the 
rollers 16 and on the bedplate 17 by sliding on them and they are driven 
by transverse torque bars 18 attached, at their ends to endless chains 19 
extending longitudinally on both side of the transfer path 15, and driven 
by a motor 21. The motor 21 is powered intermittently and the spacing 
between the torque bars 18 is chosen in such a way that, during each 
period that the motor 21 is running, each container 1 is driven from the 
stand-by station A to the film application station B or from this latter 
station onto a removal conveyor located in extension of the conveyor 2 and 
not represented. 
Upstream of the conveyor 2 with intermittent movement and in alignment with 
it, there is a selection station S comprising a supply conveyor 22 of any 
suitable type, on which are placed the containers arriving one after the 
other. This conveyor 22 is situated at a level a little lower than that of 
the support rollers 16 of the endless conveyor 2 so that the upstream end 
roller 16 forms an abutment to stop each new container 1 arriving, thereby 
causing an accumulation of containers one after the other, on the supply 
conveyor 22. A selector 23, fitted with a raising and lowering system 
controlled by a jack 24, allows, at the appropriate moment in the 
machine's cycle, the levering up to a small extent of the downstream part 
of the first container 1 in the series of containers waiting on the supply 
conveyor 22, and causes it to pass onto the bed of rollers 16 in order to 
position it at the stand-by station A. 
At the selection station S and at stations A and B there are, on one of the 
longitudinal sides of the conveyors, in this case on the right side in 
FIG. 11, longitudinal fixed guides 25 which are aligned, and which define 
a vertical and longitudinal reference plane P and against which one 
longitudinal side wall of the successive containers 1 is pressed. At the 
selection station there is also a lateral urging bar 26 which is situated 
opposite the corresponding fixed longitudinal guide 25, that is to say on 
the left side of the machine and which is transversely mobile, on slides 
27, under the command of a jack 28. When the jack 28 is actuated in the 
appropriate direction, the urging bar 26 is displaced laterally towards 
the fixed guide 25 and it presses the container 1 which is between them 
against the fixed guide 25 so that its right longitudinal side wall is in 
the longitudinal reference plane P defined by the fixed guides 25. The 
extent of the displacement of the lateral urging bar 26 is also used, in 
this embodiment of the machine, to measure the transverse dimension a of 
each container 1. The measurement of the transverse dimension a is thereby 
taken and transmitted to the general command apparatus 4 (FIG. 1) and this 
commands the transverse displacement of mobile longitudinal guides 29, 31, 
which are respectively on the left side of the machine, that is to say 
opposite the fixed guides 25, at the site of stations A and B, in such a 
way that these mobile guides 29,31, servo-driven by the urging bar 26, 
come into longitudinal alignment at the distance a from the fixed guides 
25 opposite, which corresponds to the transverse dimension a of the 
container 1 being dealt with. 
The longitudinal guides 29,31 are movably mounted on respective transverse 
slides 32, 33 and their movements are commanded by respective transverse 
jacks 34, 35. 
The height h of each container 1 is measured at the stand-by station A, by 
means, for example, of a set of superimposed photo-electric cells 36 
arranged above the conveyor 2, and on one side of it. These photo-electric 
cells 36 or any other equivalent means are connected to the general 
command apparatus 4 in order to bring about the automatic setting of the 
vertical position of the film application device as a function of the 
height h of each container 1. 
The film application station B will now be described in detailed fashion. 
The device 7 comprises, apart from the pressing head 13, a horizontal 
frame or apron 37 which is mounted in a vertically adjustable fashion on 
the base 38 of the machine. To this end, the right longitudinal side (FIG. 
11) of the frame 37 is attached to a pair of vertical endless chains 39, 
movably mounted on the base 38 and driven by a motor 41 in such a way that 
the frame 37 can be vertically displaced and placed in a vertical position 
close to the top edge of each container 1 that is under it at station B, 
whatever the height h of this container may be. 
The frame 37 carries several mobile assemblies. In a first place, in this 
non-limitative embodiment, it carries, on its upstream transverse side, 
nozzles that form part of the glue application device 6, the longitudinal 
position of which is fixed. More particularly, the glue application device 
comprises at least one vertical nozzle 42 and preferably two nozzles which 
are mounted in fixed positions on the frame, on the right side on FIG. 11, 
that is to say on the side of the vertical reference plane P, in such a 
manner that they project, onto the bottom of each container 1, pressed 
against the fixed reference guide 25, during its longitudinal displacement 
from station A to station B, one or two longitudinal strips of glue 12. To 
this end, the axes of the fixed nozzles 42 are slightly offset towards the 
interior, in relation to the fixed guides 25, in such a way that they 
project their jets of glue to the appropriate places on the bottom of each 
container 1. The glue application device 6 also comprises, at the same 
level as the fixed nozzle or nozzles 42, one or two opposite nozzles which 
are mounted in a transversely mobile fashion on the frame 37, under the 
command of at least one jack 44. The transverse position of the nozzle 43 
or of each nozzle 43 can thus be adjusted as a function of the transverse 
dimension a of the container 1 that is under the frame 37. The nozzles 42, 
43 are supplied with glue under pressure, during the longitudinal 
displacement of each container underneath them, under the command of a 
photo-electric cell that detects the passage of the container, the 
duration of the projection of the jets of glue being about 2 seconds. 
The frame 37 also carries means that allow the transverse drawing of the 
plastic film 9 over the container 1. These means comprise the longitudinal 
mobile grip 8 which extends longitudinally and which is displaced 
transversely by transverse endless chains 45 movably mounted on the frame 
37 and driven by a motor 46. The frame 37 also carries, on its right part, 
that is to say on the side of the vertical reference plane P, a 
longitudinal grip 47 in a fixed position. The opening and the closing of 
the mobile grip 8 and of the fixed grip 47 are caused by jacks which are 
themselves actuated by the general command apparatus 4 (FIG. 1). 
The plastic film is unwound from the roll 11 which is situated on the right 
side of the machine at station B, and which is rotatably driven by a motor 
48. The unrolled film 9 passes into a hoisting device 49 which includes 
fixed rollers 51 and mobile rollers 52 supported by an articulated arm 53 
pivoting about a spindle 54. After having passed through the hoisting 
device 49, the film is taken up by the fixed grip 47. The unwinding of the 
roll 11 occurs between two cycles, while the end of the film 9 is held by 
the closed fixed grip 47. The articulated arm 53, mechanically commanded, 
carries out a downward rotation causing a certain length of film 9, 
constituting an available reserve of film, to be unwound. During the 
insertion of the film 9 into the container 1 by the pressing head 13, this 
allows the arm 53 of the hoisting device 49 which is then made free 
without any constraint, to come back to its high position under the effect 
of the traction of the film 9, as is shown in FIG. 11. 
The frame 37 also carries the cutting device 14. This cutting device 14 
comprises a vertical knife 55 which is situated proximate to the fixed 
grip 47, towards the inside. The knife 55 is rigidly fixed to an endless 
chain 56 extending horizontally and longitudinally, which is driven by a 
motor 57, in such a way that it can cut the film 9, in the transverse 
direction of this film, during the time at the end of it being pressed 
onto the bottom of the container 1. 
As has been previously indicated, the film application device 7 also 
comprises, above the central opening of the frame 37, the pressing head 13 
which is vertically and movably mounted on the base 38 of the machine. 
This pressing head 13 is rigidly fixed to a vertical arm 58 sliding in a 
vertical slide 59 rigidly fixed to a bracket 61. This bracket 61 is 
attached to vertical endless chains 62 which are supported by the base 38 
and which are driven by a motor 63. When the motor 63 is switched on, in 
the appropriate direction, by the general command apparatus 4, this causes 
vertical movement of the pressing head 13 in order to lower it, through 
the central opening of the frame 37, to the inside of the container 1, so 
as to press the film 9 onto the glued bottom of the container, and in 
order to cause it to rise again, after pressing above the frame 37 as 
represented in FIG. 11. 
The pressing head can have a constant transverse dimension, if the 
transverse dimension a of the containers does not vary, or contrary to 
this it can be variable in the case where the machine operates with 
containers with a variable transverse dimension a. In this latter case, 
the pressing head 13 is extendible in the transverse direction and a 
non-limitative embodiment of this head is represented in FIGS. 12 and 13. 
The pressing head 13 includes in its lower part, two L-shaped pressing 
elements, namely a fixed pressing element 64 and a transversely mobile 
pressing element 65, each comprising a respective vertical plate 64a, 65a 
and a respective horizontal plate 64b, 65b. Each of the horizontal plates 
64b, 65b which extend one towards the other, of the pressing elements 64, 
65 is advantageously provided with a layer of an elastic material 66 such 
as a layer of foam on its lower face. The mobile pressing element 65 is 
displaced transversely under the command of a jack 67 by using a linking 
mechanism 68 with pivoting connecting rods and with slides, as is shown in 
FIGS. 12 and 13. Actuation of the jack 67, in one direction or in the 
other allows the pressing head 13 to be extended or retracted in the 
transverse direction so as to adapt it to the transverse dimension a of 
the container 1. At the time of the descent of the pressing head to the 
inside of the container 1, the horizontal plates 64b, 65b are applied, 
with the lower layers of foam that they are carrying, onto the film 9 
which extends horizontally and they drive it downward as far as the bottom 
of the container 1, the head 13 is immobilized in the pressing position 
while the bracket 61 continues its descending travel. The plates 64b, 65b 
exert a pressure on the film 9 which is applied onto the strips of glue 12 
previously deposited onto the bottom of the container. 
In the case where the container 1 is a cardboard box with internal bottom 
flaps that are not joined, the layers of foam 66 advantageously have in 
their middle parts, transverse bosses 66a (FIG. 10) the width of which 
approximately correspond to the distance between the edges of the internal 
flaps, so as to be able to effectively press the film into the space 
between the edges of the internal flaps. 
Advantageously the machine also comprises small air blowers which are 
associated with the film application device 7 and which allow one to fold 
back to the inside of the container the free end parts of the section of 
thermo-plastic film, only the central part of which is stuck to the 
bottom. 
The machine according to the invention allows one to achieve a high rate of 
production of the order of 660 to 720 containers per hour, or 10 to 12 
containers per minute.