MANIPULATOR FOR MANIPULATING OVER-EDGES OF A PLASTIC FILM WRAPPED ON CONTAINERS FOR MAKING A BUNDLE OF CONTAINERS, APPARATUS COMPRISING SUCH MANIPULATORS AND RELATIVE CONTROL METHOD

Abstract

Manipulator for manipulating over-edges of a plastic film wrapped on containers for making a bundle of containers of the type including a vertical support rod provided with a motorization for rotating around own vertical axis. The rod supports a mechanism for stretching and drawing said over-edges alongside said containers; and a device for pressing the over-edges against the containers. The device for stretching and for drawing alongside and he device for pressing are arranged one above the other along the development of the vertical support rod.

Description

The present invention relates to a manipulator for manipulating a plastic film wrapped on containers for making a bundle of containers.

The present invention also relates to a control method of said device and to an apparatus for making a bundle comprising such devices.

Particular product packages/containers are currently known and available on the market, called bundles, which in extreme synthesis correspond to a plurality of products arranged ordered along at least one row and wrapped in a heat-shrunk film.

The methods currently known for making a bundle as described above therefore include the steps of:

• • arranging an open tunnel of heat-shrinkable film around a group of containers ordered along at least one row so that the heat-shrinkable film has, orthogonally to the longitudinal advancement direction, over-edge portions with respect to the overall dimensions of the containers;
  • feeding the containers and heat-shrinkable film to a heat treatment device, i.e. a convection oven, so that the over-edge portions compact on the containers by heat-shrinking.

EP2219954 describes a method for making a bundle wherein the step of manipulating the over-edge portions involves the ordered folding of the over-edges on themselves so as to achieve, post-heat-shrinking, the total closing of the lateral portions of the bundle. According to other prior arts, less sophisticated than that described in EP2219954, the step of manipulating the over-edge portions only involves the lifting/orientation of the over-edges so that post-heat-shrinking, they compact on the lateral front portions of the bundle leaving more or less regular lateral openings.

The second prior art just described above is currently the most widely used because it requires less consumption of films and because it is more easily implemented.

Again this technique provides that, by varying the size of the containers, the film needs to be replaced to always ensure a large over-edge, as well as the fact of using a film having a differentiated heat-shrinkage. That is, the film should have a heat-shrinking:

• • approximately 50% to 80% longitudinally according to the bundle advancement direction;
  • approximately 0% to 35% transversally/orthogonally to the bundle advancement direction.

The prior art described has some drawbacks, such as, for example, the presence of wrinkles on the finished bundle right at the adhesion zones of the over-edges. Such wrinkles that are generated during the heat-shrinking of the over-edges in convection ovens can in fact affect the handling of the finished bundle or make it more difficult.

In order to implement a method for making a bundle that requires less consumption of film without impairing the stability of the bundle and without making any wrinkle, the Applicant has previously developed apparatus able to control the arrangement of the over-edges with respect to the containers, making the film adhere with glue on the products already upstream of the heat-shrink oven.

In this way, heat-shrinking can be defined as controlled.

As it is comprehensible, in this way the heat-shrinking of the over-edges takes place in a more controlled manner as the film is already suitably arranged around the lateral portions of the products.

This innovation implemented by the Applicant has allowed making a controlled heat-shrinking bundle whose film can have orthogonal dimension with respect to the advancement of the bundle which is reduced from 10% to 35% compared to a conventional bundle produced by the prior art.

In addition to lower consumption, the above controlled heat-shrinking allows using a film with heat-shrinking factor orthogonal to the advancement direction of the bundle close to zero.

This type of film allows eliminating the wrinkles that may normally be formed in this process step.

Therefore, since the manipulation of the over-edges becomes relevant to the quality of the finished product, with the present invention the Applicant aims to provide appropriate means able to manipulate the over-edges before the oven so that they are effectively constrained to the containers along the spots where glue has been previously supplied.

The features and the advantages of a method of making a bundle according to the present invention will become clearer from the following exemplary and non-limiting description, made with reference to the accompanying schematic drawings, in which:

FIG. 1 shows a first production step of the bundle upstream of the heat-shrinking oven;

FIG. 2 shows a second production step of the bundle upstream of the heat-shrinking oven;

FIG. 3 shows the finished bundle downstream of the hear-shrinking oven;

FIG. 4 shows a first embodiment of the means able to manipulate the over-edges according to the present invention;

FIGS. 5A and 5B show enlarged details of the means for manipulating the over-edges in FIG. 4;

FIG. 6 shows an example of a manipulation station of the over-edges with a series of manipulation means according to the present invention;

FIGS. 7-11 show the movements of manipulation means according to the present invention with respect to a bundle during the manipulation steps; and

FIG. 12 shows an apparatus provided with the manipulators according to the present invention. With reference to the figures, a bundle of containers, bottles, cans, multipacks, cluster packs, boxes, etc. is indicated with reference number 10 and the means able to manipulate the over-edges according to the present invention are indicated with reference number 100.

Such a bundle 10 is of the type comprising a plurality of containers 11 arranged along at least one row, preferably two, and wrapped in a film 12, in particular a heat-shrinkable film.

The steps to make such a bundle can be summarized with the steps of:

a) arranging a heat-shrinkable film 12 around the ordered containers 11 in such a way as to create an open tunnel 13 along the transverse direction 20 with respect to the longitudinal advancement direction 20′;

such an open tunnel 13 defines side over-edge portions 14 with respect to containers 11 along the transverse direction 20;

b) manipulating the over-edge portions 14;

c) feeding containers 11 and the manipulated heat-shrinkable film 12 to a heat treatment device so that the over-edge portions 14 compact to containers 11 by heat-shrinking.

Advantageously and preferably, the step of manipulating the over-edge portions 14 comprises the step of adhering at least partially the over-edge portions 14 to the containers 11 upstream of the heat treatment device at at least one glue spot dispensed on the front container and on the rear container on both sides of the bundle.

In FIG. 1, the glue spots are indicated with reference numeral 23 and may include a single spot or a series of glue spots along the vertical direction. The heat treatment device is a convection oven, while tunnel 13 may be the combination of multiple sheets of film 12 folded on themselves.

In FIG. 2, reference numeral 21 schematizes the technical means currently known in the form of prongs adapted to bring the over-edge portions 14 in contact with the front and rear portions of containers 11.

This constraint, as mentioned above, is ensured by glue 23 arranged in a spot-like manner by means of nozzles spraying on containers 11 and/or on film 12.

Since by means of the glue spraying nozzles it is possible to dispense a series of glue spots along the vertical direction, with the same machinery it is possible to treat containers of different heights.

An upper stabilizing device is schematically shown with reference number 22.

Bundle 10 obtained by the method described has peculiar features, such as the absence of wrinkles and/or the presence of constraint points 23 between film 12 and containers 11.

According to the present invention, prongs 21 are replaced by specific means 100 adapted to bring the over-edge portions 14 in contact with the front and rear portions of containers 11 at the glue spots dispensed before.

Such innovative manipulators 100 of the over-edges, which are supported on a movable structure which will be described hereinafter, include:

• • means for stretching and drawing 101 the film alongside the bottle by a considerable portion of vertical flap around the glue spot 23, for example in the form of at least one brush 101; and
  • means for pressing 102 the film at the glue spots to compress the same so that from a glue spot 23 (2-3 mm diameter) with a certain relief an areola is obtained (7-10 mm diameter) with small thickness.

The compression of the glue spots 23 is needed for both mechanical reasons, in fact doing so results in a stronger bonding, and for aesthetic reasons to reduce the above relief at the glue dispensing spots. More in detail, the means for pressing 102 film 12 include two functional portions, namely:

a) a glue-presser cam 104 which contacts film 12;

b) an elastic element 105 supporting the cam.

The glue-presser cam 104 is preferably made of Teflon for two reasons, namely because this material has low dry sliding friction and due to its non-adhering properties with respect to glue.

Advantageously, therefore, in case of accidental contact between glue 23 and cam 104, the latter can be cleaned in a few cycles of the machine thus producing a self-cleaning cam.

The elastic element 105 supporting the cam may be made with one or more bending springs connected to the glue-presser cam 104, as shown in the figures, or it may possibly be integral with cam 104 in the form of a simple elastic sheet.

The elastic support 105 is necessary to compensate possible positioning errors and the dimensional variability of the containers themselves.

Operatively, during the test and setting step of the container size to be worked, the penetration parameter of the cam with respect to the container is established, indicated with “C” in FIG. 7. This parameter in practice realizes a sort of nominal preload of the leaf spring 105.

As shown in FIG. 6, cam 104 and brush 101 are integral to each other and can be adjusted in height by loosening respective knobs 106 and moving carriage 107 along a vertical graduated rod 108.

The vertical support rod 108 rotates around its vertical axis by means of an independent servomotor 109 placed at the upper end of the rod 108 itself.

Four over-edge manipulation means 100 as described above act simultaneously on each transiting bundle. The rotary actuators 109 of the two front manipulation means 100 are mounted on an independent front carriage 110 moving in the longitudinal advancement direction of the bundles.

Likewise, the rear manipulation means 100 are mounted on an independent rear carriage 111 (FIG. 12). In the configuration with two tracks, FIG. 12, it is necessary to operate on two bundles offset by one step since, otherwise, the central systems of the tracks would collide.

In order to adjust to size, each rotary actuator is positioned at the transversal dimension defined along the transverse guides 112.

The adjustment in the longitudinal direction is completely automatic since the two carriages 110, 111 are driven by independent servomotors and adapt automatically to the length of the bundle.

Before describing the unit movement in a qualitative manner, the following definitions are provided:

a) the movements of the carriages 110, 111 linked by an electronic cam are periodically alternating;

b) group in phase with the package transiting: in this advancement condition, the transverse plane of symmetry between two manipulators, one mounted on the front carriage 110 and the other on the rear one 111 coincides with the transverse plane of symmetry of the package to be treated in transit at constant speed v=f*p (mm/s), where “f” and “p” are respectively the frequency in (Hz) and the machine pitch in (mm) (FIGS. 8 and 9);

c) actuators at maximum center distance “Imax”; maximum distance during motion between the two front and rear manipulators; it takes place during the motion step between the zero position of the manipulators and the coupling position in phase (see FIG. 9);

d) actuators at minimum center distance “Imin”; minimum distance during motion between the two front and rear manipulators; it takes place upon reaching the condition of gluing of the film on the product (see FIG. 8);

e) zero position of the manipulators of over-edges 100; the manipulators are rotated as in FIG. 8 with cam 104 arranged parallel to the movement sense (20′);

f) gluing position; cams 104 are rotated by 90° as shown in FIG. 8;

g) bundle receipt position; manipulators 100 are positioned with the actuators at distance Imax, in all back position, with speed equal to zero; the transverse plane of symmetry between front and rear manipulators is more advanced by a distance “ANT” than the plane of symmetry of the approaching package (FIG. 10). From this condition, i.e. with this advance “ANT”, the manipulators start moving to bring carriages 110 and 111 in phase with the package in transit after the acceleration step (speed coupling step).

Then, carriages 110, 111, which start from the configuration of FIG. 10 at zero speed, with synchronous motion reach that of FIG. 9 with speed “v” equal to that of the bundle in transit.

At this point, the rotating movement of the manipulators begins with concurrent relative approach motion to the bundle of the axes of rotation of the manipulators. The center distance ranges from Imax to Imin.

The latter movement is necessary because the rotation of the manipulators alone would result in a non-optimal folding of the over-edge and would lack the stretching effect of the film 12 on the product.

Upon reaching the closed position, FIG. 8, this is maintained for a very short time, even zero, since it affects the maximum acceleration and speeds of all other moving parts. By testing, the Applicant has verified that the quality of gluing is affected more by the geometry of the glue-presser cam 104, its rigidity, its closing movement and its disengagement (see next point) than by the pressure time.

During the disengagement movement, the manipulators further rotate by an angle necessary to release from the contact with the bundle, achieving the configuration in FIG. 11.

This is necessary in order to carry out the subsequent motions that will no longer be in phase with the bundle, that is, the deceleration of carriages 110, 111 which, starting from the configuration in FIG. 11, slows down going from speed “v” to zero so as to then make a return movement to the zero position of the group of FIG. 10.

In this step, there occurs the return stroke of both carriages 110, 111 up to reach the zero position again. During this step, when the manipulators are outside of the encumbrance of the bundle in transit and before entering the encumbrance of the next package, the rotating motion of the same is launched up to the zero position.

The synchronized movements of the manipulators, referred to as “electronic cam” above, are fully parameterized and therefore all the motion steps can be configured as desired.

It has thus been seen that the manipulators according to the present invention achieve the objects set forth above, i.e., offer a valid alternative to those known today and are particularly performing even in case of little over-edge.

The device of the present invention thus conceived can be subjected to numerous modifications and variants, all falling within the same inventive concept; moreover, all details may be replaced with technically equivalent elements. In the practice, the materials used as well as the dimensions thereof may be whatever, according to the technical requirements.

Claims

1. A manipulator for manipulating over-edges of a plastic film wrapped on containers for making a bundle of containers of the type comprising a vertical support rod provided with a motorization for rotating around own vertical axis; said rod supporting: means for stretching and drawing said over-edges alongside said containers; andmeans for pressing said over-edges against said containers;wherein said means for stretching and for drawing alongside and said means for pressing are arranged one above the other along the development of said vertical support rod.

2. The manipulator according to claim 1, wherein said means for stretching and drawing alongside can comprise a brush.

3. The manipulator according to claim 1, wherein said means for stretching and drawing alongside comprise two brushes respectively arranged above and below said means for pressing said over-edges against said containers.

4. The manipulator according to claim 1, wherein said means for pressing comprise a glue-presser cam and an elastic element connecting said cam to said vertical support rod.

5. The manipulator according to claim 1, wherein said means for stretching and drawing alongside and said means for pressing are integrally movable along said vertical support rod and constrainable at a variable height.

6. An apparatus for making a bundle of containers comprising: means for manipulating and orienting said containers and said film configured for arranging said containers ordered along at least one row inside an open tunnel of heat-shrinkable film along the direction orthogonal to the longitudinal advancement direction of said bundle, said open tunnel having over-edges portions lateral with respect to said containers;means for manipulating said over-edges portions configured for constraining said over-edge against said containers at said glue spots; andmeans for the heat treatment of said bundle, so that said over-edges portions compact to said containers by heat-shrinking;wherein said means for manipulating said over-edge portions are arranged upstream of said thermal treatment means; andwherein said means for manipulating said over-edges portions comprise four manipulators according to claim 1 configured for operating at the four vertices of said bundle.

7. The apparatus according to claim 6 wherein said four manipulators are mounted on two independent carriages, respectively two front manipulators on a front carriage movable in the longitudinal advancement direction of the bundles and two rear manipulators mounted on an independent rear carriage.

8. The apparatus according to claim 6 wherein it comprises two tracks wherein said manipulators are offset.

9. The apparatus according to claim 6 wherein it comprises transverse guides for the transverse adjustment of said manipulators.

10. A method for manipulating the over-edges in an apparatus by means of manipulators according to claim 1 comprising the steps of: positioning the manipulators at a maximum distance with cams parallel to the movement sense with velocity equal to zero;starting moving the carriages when the transverse symmetry plane between the front and the rear manipulators is more advanced than a preset distance with respect to the symmetry plane of the bundle approaching at a velocity “v” until leading said carriages in phase with said passing bundle;rotating the manipulators with simultaneous relative approaching movement of the rotation axes to the bundle and reduction of the minimum center distance (Imin) up to a contact with theoretical penetration;disengaging the manipulators by further rotating by an angle to lead the cams outside the volume of said bundle;decelerating the carriages to zero velocity and performing a return movement to the starting position of the axes of the manipulators; androtating the manipulators until the starting condition is restored.

11. The manipulator according to claim 2, wherein said means for pressing comprise a glue-presser cam and an elastic element connecting said cam to said vertical support rod.

12. The manipulator according to claim 3, wherein said means for pressing comprise a glue-presser cam and an elastic element connecting said cam to said vertical support rod.

13. The manipulator according to claim 2, wherein said means for stretching and drawing alongside and said means for pressing are integrally movable along said vertical support rod and constrainable at a variable height.

14. The manipulator according to claim 3, wherein said means for stretching and drawing alongside and said means for pressing are integrally movable along said vertical support rod and constrainable at a variable height.

15. The manipulator according to claim 4, wherein said means for stretching and drawing alongside and said means for pressing are integrally movable along said vertical support rod and constrainable at a variable height.

16. An apparatus for making a bundle of containers comprising: means for manipulating and orienting said containers and said film configured for arranging said containers ordered along at least one row inside an open tunnel of heat-shrinkable film along the direction orthogonal to the longitudinal advancement direction of said bundle, said open tunnel having over-edges portions lateral with respect to said containers;means for manipulating said over-edges portions configured for constraining said over-edge against said containers at said glue spots; andmeans for the heat treatment of said bundle, so that said over-edges portions compact to said containers by heat-shrinking;wherein said means for manipulating said over-edge portions are arranged upstream of said thermal treatment means; andwherein said means for manipulating said over-edges portions comprise four manipulators according to claim 2 configured for operating at the four vertices of said bundle.

17. An apparatus for making a bundle of containers comprising: means for manipulating and orienting said containers and said film configured for arranging said containers ordered along at least one row inside an open tunnel of heat-shrinkable film along the direction orthogonal to the longitudinal advancement direction of said bundle, said open tunnel having over-edges portions lateral with respect to said containers;means for manipulating said over-edges portions configured for constraining said over-edge against said containers at said glue spots; andmeans for the heat treatment of said bundle, so that said over-edges portions compact to said containers by heat-shrinking;wherein said means for manipulating said over-edge portions are arranged upstream of said thermal treatment means; andwherein said means for manipulating said over-edges portions comprise four manipulators according to claim 3 configured for operating at the four vertices of said bundle.

18. An apparatus for making a bundle of containers comprising: means for manipulating and orienting said containers and said film configured for arranging said containers ordered along at least one row inside an open tunnel of heat-shrinkable film along the direction orthogonal to the longitudinal advancement direction of said bundle, said open tunnel having over-edges portions lateral with respect to said containers;means for manipulating said over-edges portions configured for constraining said over-edge against said containers at said glue spots; andmeans for the heat treatment of said bundle, so that said over-edges portions compact to said containers by heat-shrinking;wherein said means for manipulating said over-edge portions are arranged upstream of said thermal treatment means; andwherein said means for manipulating said over-edges portions comprise four manipulators according to claim 4 configured for operating at the four vertices of said bundle.

19. An apparatus for making a bundle of containers comprising: means for manipulating and orienting said containers and said film configured for arranging said containers ordered along at least one row inside an open tunnel of heat-shrinkable film along the direction orthogonal to the longitudinal advancement direction of said bundle, said open tunnel having over-edges portions lateral with respect to said containers;means for manipulating said over-edges portions configured for constraining said over-edge against said containers at said glue spots; andmeans for the heat treatment of said bundle, so that said over-edges portions compact to said containers by heat-shrinking; andwherein said means for manipulating said over-edge portions are arranged upstream of said thermal treatment means;wherein said means for manipulating said over-edges portions comprise four manipulators according to claim 5 configured for operating at the four vertices of said bundle.