CA1079618A

CA1079618A - Device for sealing wraps made of thermoplastic material, particularly on machines that overwrap, for example, packets of cigarettes or similar

Info

Publication number: CA1079618A
Application number: CA231,216A
Authority: CA
Inventors: Enzo Seragnoli
Original assignee: GD SpA
Current assignee: GD SpA
Priority date: 1974-07-10
Filing date: 1975-07-10
Publication date: 1980-06-17
Also published as: BR7504121A; CH589536A5; GB1515145A; JPS5131582A; FR2277729B1; SE7507853L; IT1018093B; AT345739B; DE2528594A1; AR208196A1; NL7508049A; ES439404A1; FR2277729A1; SU618024A3; ATA486775A; DD119996A5; PL103016B1; CS201530B2; SE422041B

Abstract

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ABSTRACT OF THE DISCLOSURE
The present invention provides an apparatus for sealing wraps made of thermoplastic material, particularly on machines that overwrap, for example, packets of cigarettes, on which it is possible to match the characteristic requirements of the said thermoplastic material with those experienced when using the material on very high output speed overwrapping machines, i.e., with the requirements for the temperature of the sealing devices to be restored very rapidly after each sealing operation and for the temperature in the vicinity of each sealing area to be continuously checked. The sealing apparatus comprises a body that is essentially of wedge shape with its vertex constituting the sealing extremity pointing towards the wrapping line and extending so as to keep in the immediate proximity of the said vertex, a source of heat and a terminal of a probe for measuring and checking the temperature; plates of thermally insulated material being provided, shaped to be insertable, at the time of sealing, between the said body, up to the immediate vicinity of the contact area of the said sealing extremity, and the thermoplastic wrap.

Description

The present invention relates in general to wrapping or packaging machines and, in particular, to overwrapping machines, i.e., machines which wrap products previously packed in wraps that are essentially parallelepiped in shape in transparent ~ ;
sheets.
For reasons of hygiene, as well as pleasant appearance, packets of cigarettes are, in particular, usually wrapped and sealed in sheets of transparent paper on overwrapping machines of the type mentioned above.
The wrapping style normally used for the said products is that known as the "soap style" and according to the art, to - hermetically seal the wrapping material calls for sealingoperations on one longitudinal side and on the two opposite ends .; .
of each packet.
For some time now increasing use has been made on the said machines of a plastic, heat-sealing type of wrapping material, such as, for example, that marketed under the trademark ; "Hercules" which, in comparison with conventional materials for example, the material sold under the trade mark "Cellophane"
0 offers numerous advantages but which, especially at the time the .
sealing operation is being performed on the wraps, has certain requirements.
The advantages are in brief, that the "Hercules"
(a trademark) type of material is cheaper than "Ceilophane"
(a trademark) and as it is thinner, reels of the same size last much longer.
The disadvantages arise in the temperature limits, which, for the said material, are somewhat more rigid than is the case with, for example, "Cellophane" (a trademark), being exceeded during the heat sealing operation. Above the maximum temperature limit, the material shrinks considerably and consequent ugly folds are formed which, particularly with packets of w are called the "soft cup" type, can cause crushing.
Further disadvantages due to the particular sensitivity to heat of the said thermoplastic material is, however, encounter-ed during the heat-sealing operation, even when effected under optimum temperature, pressure and contact time conditions.
Whilst, with "Cellophane" (a trademark) fusing only affects, as is known, the outer layers of the moisture proof lacquer at the time heat is being applied on the part of the sealing apparatuses and not the internal viscose support, in the case of thermoplastic materials the fusing affects the entire thickness thereof. It is, therefore, clear that buckling, which is an inevitable result of this particular operation, is a lot more noticeable on these `, materials. Defects of this nature are to be found in the areas ~, subjected to the direct action of the sealing apparatuses and inthe surroundin~ areas which defects are in the form of contraction, curling and folds in the wrapping material.
The technique used in the art aims at eliminating or at least minimizing, the aforementioned difficulties by carefully localizing the heat supplied by the sealing devices 2Q to a very limited number of areas on the wraps but in a way which is sufficient to guarantee the sealing operations being perfectly successful. For example, sealing apparatuses have been proposed which consist of fixed chambers that contain a source of heat and are provided with one or more narrow apertures at a point where there is a wall which serves, not only as a means -i of thermal insulation but also as a guide for the pile of packets wrapped in their thermoplastic wraps which are intermittently moved.
During the stationary periods of the pile, the sealing operation takes place on the areas of the wrap located adjacent the apertures communicating with the said chamber. The source -of heat, positioned so as to be able to uniformly supply the various distribution points consists, for example, of a source of hot air or of electrical resistors. In the latter case, the sealing apparatuses are made of thin strips of metal, fixed or movable through the said apertures.
Despite the said apparatuses, the use of thermoplastic materials on very high output speed overwrapping machines can cause the previously described disadvantages to be enhanced and new requirements for the satisfactory outcome of the sealing operation are created.
With particular reference, for example, to the over-wrapping machine for wrapping packets of cigarettes in sheets of transparent material, known commercially as the "CELL-PACK", ; (a trademark) the packets of cigarettes on this machine follow one another in succession along an intermittently movable wrapping line, at various speeds, to be subjected, at a plurality of stations, variable to suit their speed, to the action of sealing devices connected to means adapted to operate them with a reciprocating motion.
An immediate result of the high frequency of the seal-ing operations on the said machines is the possibility, when using apparatuses of known type, that the temperature of the Ir sealing apparatuses may drop, over a short time, below the lower acceptable limit for fusing the thermoplastic material.
It is, therefore, necessary not only to provi~e apparatuses having a greater flexibility, in order that the sealing operation be successful on the very high speed machines r ' but also to continuously check the temperature in the immediate vicinity of the sealing areas.
Again with reference to the use of this particular wrapping material, this is all the more necessary since machines of the above mentioned type are able to operate at varous speeds and at their lower speeds the sealing apparatuses, for obvious reasons, are heated to an extent which is in excess of the maximum temperature limit, which res~lts in damage to the wraps.
The present invention provides an apparatus for sealing wraps made of thermoplastic type wrapping material, on which it is possible to match the characteristic requirements of the said thermoplastic material with those encountered when using the device on very high output speed overwrapping machines, i.e., -' with the requirement for the temperature of the sealing devices to be restored very rapidly after each sealing operation and the possibility for the temperature adjacent of each sealing area to be continuously checked.
i The present invention thus provides a heat sealing ! device for heating sealing seams on thermoplastic overwraps on packets, the heat sealing device being positioned adjacent to a sealing station of a wrapping wheel operable at different speeds and subjected to periodic halts, and being movable into and away from contact with said seams, the device comprising a wedge shaped body having a narrow heat sealing face directed towards said seams, a source of heat adjacent the narrow heat sealing face, a probe for measuring and controlling the temperature prevailing at the narrow heat sealing face, and plates of thermally insulating material disposable between the body and overwraps, laterally of and adjacent the narrow heat sealing face, to prevent heat radiation from the body to the overwraps.
~he present invention will be further illustrated by way of the accompanying drawings which show an apparatus according to one embodiment of the present invention mounted in two different ways on the same wrapping line of the aforesaid "CELL-PACK" overwrapping machine. In the accompanying drawings ; .:. .
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Fig. 1 is a side view of a wrapping wheel of said overwrapping machine and provided with the ~ according to one embodiment of the present invention;
Fig. 2 is a view perpendicular to the direction in which it moves forward, of the exiting channel of the said over-a~rd+~s wrapping machine, which is provided with the dev~ee of Fig 1.
With reference to Fig. 1, a wrapping wheel 1 is inter-mittently rotatable in a clockwise direction on a horizontal shaft 2. The wheel 1 is provided with six radial compartments 3 and when each of these is stationary at a point corresponding to the location of an entry station I, a packet of cigarettes p is inserted therein edge on with respect to the shaft 2, together with a sheet S of transparent thermoplastic material for the formation of the outer wrap. The; two ends of the sheet of wrapping material S that protrude radially from the said wheel 1 are then folded onto the external side of the packet P by a movable folding member 4 and by a fixed folding member constituted by the inlet edge of a fixed guide S which extends along the periphery of the said wheel 1 for approximately 180, up to where a pusher 6 expeIs the packet from an ejection station.
Corresponding to the location of a second station II
and a third station III, the guide 5 is broken and two sealing devices 7 and 7' operate. The sealing devices 7 and 7', fixed to support means 8 and 8', respectively, reciprocation with respect to the edge of the wheel 1 by means of shafts 9 and 9', respectively, which are parallel with the shaft 2 and oscillate around their own shafts. The sealing contrivances 7 and 7' com-prise bars with a substantially wedge shaped section with the ; vertex, constituting the sealing extremity, pointing towards the wrapping wheel 1. This particular configuration allows the sealing to take place where there is a narrow longitudinal strip on the external side of each packet and, at the same time, 10796~8 a heat source 10 (10') which may be,~for example, an electrical resistor and the terminal of a probe 11 (11') for measuring the temperature, to be inserted in the body of each sealing device ~`c /~/~
7 (7') in the immediate vacil.iLy of its sealing extremity.
Such features have resulted in the very rapid restoration of the temperature and in the ability to constantly check the temperature in the sealing devices during the operation of the overwrapping machine at its various speeds.
Finally, two plates 12 and 12' of insulating material are fixed to the guide 5 and extend over the external sides of the packets P, except in the area in which the sealing devices 7 and 7' operate. These plates 12 and 12' protect the parts of the wrap close to the sealing area against the heat irradiated by the surfaces of the sealing devices.

In Fig. 2, which illustrates a second application for ~ ratU~ -the ~cv~ of the present invention, a section of a channel 13 constituting the exit on the overwrapping machine is shown.
At a point corresponding to this section, two opposite sealing de~ices 14 and 14' seal the two ends on the packets moving inter-, 20 mittently forward and disposed flat on the bottom of the said ;,i -: :
channel 13. Exactly as with the sealing devices 7 and 7' of Fig. 1, through their support means 15 and 15 !, respectively, the sealing devices 14 and 14' are given a reciprocating movement with respect to the walls of the channel 13. The devices 14 and 14' are also provided with a source of heat 10 (10') and with ~ a probe 11 (11') in the immediate vicinity of their sealing -` extremities. Plates 16 and 16' which extend substantially in ; contact with the two ends at a point corresponding to the said section and are provided with a slit to allow the sealing devices 14 and 14' to operate, carry out the same task as that described in respect of the plates 12 and 12'. By way of an example, the insulating plates 12-12' and 16-16' have been shown in a fixed :. . . . . .
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10796~8 position with respect to the wrapping line i.e. wheel 1 and channel 13 and to the sealing devices 7-7' and 14-14', respective-ly, but they can be movable in any manner, in such a way as to be in the positions shown at the time of the contact for the seal-ing operation between the sealing devices and the outer wrap of heat-sealing material.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A heat sealing device for heating sealing seams on thermoplastic overwraps on packets, the heat sealing device being positioned adjacent to a sealing station of a wrapping wheel operable at different speeds and subjected to periodic halts, and being movable into and away from contact with said seams, the device comprising a wedge shaped body having a narrow heat sealing face directed towards said seams, a source of heat adjacent the narrow heat sealing face, a probe for measuring and controlling the temperature prevailing at the narrow heat sealing face, and plates of thermally insulating material dispos-able between the body and overwraps, laterally of and adjacent the narrow heat sealing face, to prevent heat radiation from the body to the overwraps.

2. A heat sealing device according to claim 1, in which the plates are stationary relative to said body and said overwraps.