US20150298844A1

US20150298844A1 - Incision unit to manufacture a single-dose break-open package

Info

Publication number: US20150298844A1
Application number: US14/693,552
Authority: US
Inventors: Christian Burattini
Original assignee: EASYSNAP TECHNOLOGY Srl
Current assignee: EASYSNAP TECHNOLOGY Srl
Priority date: 2014-04-22
Filing date: 2015-04-22
Publication date: 2015-10-22
Also published as: EP2944579A3; EP2944579B1; EP2944579A2

Abstract

A unit for the incision of a strip made of a plastic material to cut two distinct incisions into two opposite surfaces of the strip; the incision unit has: a conveying device, which feeds the strip along a conveying direction; two support plates, which are arranged on opposite sides of the strip, so that each support plate faces a corresponding surface of the strip; and at least two incision devices, each of which cuts an incision into a corresponding surface of the strip and has a cutting element, which is supported by a support plate, and a contrast element, which is supported by the other support plate.

Description

FIELD OF THE ART

The present invention relates to an incision unit for a packaging machine for single-dose break-open packages.

BACKGROUND

A sealed single-dose break-open package normally consists of a sheet made of a semirigid plastic material and of a sheet made of a flexible plastic material arranged on top of and sealed to each other in order to define a sealed pocket containing a dose of product; the semirigid plastic material sheet centrally has an incision which guides a controlled breaking of the semirigid plastic material sheet. In use, in order to open the package, a user simply needs to grip the package itself with his/her fingers and bend the package until the semirigid plastic material sheet breaks at the incision.
Patent application WO2008038074A1 suggests a packaging machine which manufactures sealed single-dose break-open packages. In such a packaging machine, a strip made of a semirigid plastic material and a strip made of a flexible plastic material are unwound from respective reels and fed to a forming station. A pattern is printed on the outer surface of the semirigid plastic material strip and an incision is cut into the semirigid plastic material strip upstream of the forming station; in particular, two incisions are cut at different times (i.e. not simultaneously) into the opposite surfaces of the semirigid plastic material strip, which incisions are opposite and aligned by means of two incision devices arranged one next to the other in the conveying direction of the semirigid plastic material strip. After that, the semirigid plastic material strip and the flexible plastic material strip are arranged on top of each other in the forming station and then sealed in a longitudinal sealing station in order to define a tube adapted to contain the product. A dosing device is arranged at the longitudinal sealing station to feed the product between the two strips which were longitudinally sealed. A transversal sealing station is arranged downstream of the longitudinal sealing station to perform a transversal sealing so as to close the pocket of each sealed single-dose package. Finally, a cutting station is arranged downstream of the transversal sealing station, where the two strips are cut transversely so as to separate, in sequence, the sealed single-dose packages.
However, it has been noted that, when operating at high speed in the above-described packaging machine, the incision of the semirigid plastic material strip not always has an optimal quality (in particular, the two incisions cut into the opposite surfaces of the semirigid plastic material strip are not always perfectly aligned to each other).
It is the object of the present invention to provide for an incision unit for a packaging machine which manufactures a single-dose break-open package, which incision unit is free from the above-described drawbacks, and in particular is easy and cost-effective to be implemented.
According to the present invention, an incision unit to manufacture a single-dose break-open package is provided as defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which show a non-limiting embodiment thereof, in which:

FIG. 1 shows a top perspective view of a sealed single-dose break-open package;

FIG. 2 shows a bottom perspective view of the package in FIG. 1;

FIG. 3 shows a cross-section of a semirigid plastic material sheet of the package in FIG. 1;

FIG. 4 shows a diagrammatic perspective view, with parts removed for clarity, of a packaging machine manufactured according to the present invention for producing the package in FIG. 1;

FIGS. 5-8 are four diagrammatic top views, with parts removed for clarity, of an incision unit of the packaging machine in FIG. 4 during four different operation moments;

FIG. 9 is a diagrammatic section view, with parts removed for clarity, of a printing unit of the packaging machine in FIG. 4; and

FIG. 10 is a diagrammatic perspective view, with parts removed for clarity, of a dosing unit of the packaging machine in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2, reference numeral 1 indicates as a whole a sealed single-dose break-open package. Package 1 comprises a sheet 2 made of a semirigid plastic material and rectangular in shape, and a sheet 3 made of a flexible plastic material, which is arranged on top of and sealed to the semirigid plastic material sheet 2 in order to define a sealed pocket 4 containing a dose of a fluid product 5. By way of example, the fluid product 5 could be a sanitizing gel.
The semirigid plastic material sheet 2 centrally has a pre-weakened zone 6 which guides a controlled breakage of sheet 2 so as to determine the formation of an outlet opening for product 5 through sheet 2. In other words, in use, in order to open package 1 a user needs to grip package 1 with his/her fingers and bend package 1 until the semirigid plastic material sheet 2 breaks at the pre-weakened zone 6.
As shown in FIG. 3, the pre-weakened zone 6 comprises an internal incision 7 which is cut through an inner surface 8 (i.e. facing pocket 4) of the semirigid plastic material sheet 2 and an outer incision 9 which is cut through an outer surface 10 of the semirigid plastic material sheet 2. According to a preferred embodiment, each incision 7 or 9 is of variable depth along its length so as to determine a progressive breaking of the semirigid plastic material sheet 2; in particular, each incision 7 or 9 has a maximum depth at a central portion.
In FIG. 4, reference numeral 11 indicates as a whole a packaging machine to produce sealed single-dose packages 1 similar to that described above and shown in FIGS. 1 and 2. The packaging machine 11 shown in FIG. 4 produces three sealed packages 1 at a time, i.e. operates in parallel on three adjacent tracks to produce three sealed packages 1 at a time; according to other variants (not shown), the packaging machine 11 could obviously operate in parallel on a different number of tracks arranged one next to the other (e.g. two, four, six tracks but also a single track).
The packaging machine 11 (shown in FIG. 4) comprises a frame (not shown) resting on the floor by means of a plurality of resting feet (not shown) and supports a pair of unwinding devices 12 and 13. The unwinding device 12 supports a reel 14 from which it progressively unwinds a strip 15 of semirigid (yet elastically deformable) plastic material which is fed to a forming station 16, and the unwinding device 13 supports a reel 17 from which it progressively unwinds a strip 18 made of a flexible plastic material which is also fed to the forming station 16.
A printing unit 19 is arranged between the unwinding device 12 of the semirigid plastic material strip 15 and the forming station 16, where the outer surface 10 of the semirigid plastic material sheet 2 is printed.
An incision unit 20 is arranged downstream of the printing unit 19 and upstream of the forming station 16, and transversely cuts the semirigid plastic material strip 15 in order to define the incisions 7 and 9 at the pre-weakened zone 6 along the semirigid plastic material strip 15.
According to a preferred embodiment, the semirigid plastic material strip 15 is continuously fed through the incision unit 20; to this end, the incision unit 20 comprises a conveying device 21 provided with a pair of feeding dandy rollers 22. The feeding dandy rollers 22 are movable against the action of elastic means to allow the semirigid plastic material strip 15 to temporarily stop inside the incision unit 20.
As shown in FIG. 4, the semirigid plastic material strip 15 provided with the incisions 7 and 9 is then fed to the forming station 16, which is arranged downstream of the incision unit 20 and where the semirigid plastic material strip 15 is arranged on top of and sealed to the flexible plastic material strip 18.
The two strips 15 and 18 arranged one on top of the other are sealed to each other by means of a longitudinal roller sealing device 23 which performs a longitudinal sealing (both laterally and centrally), i.e. parallel to a conveying direction, so as to define a plurality of tubes arranged one next to the other. In the embodiment shown in FIG. 4, the longitudinal sealing device 23 comprises two twin sealing assemblies arranged one on top of the other, each of which has a contrast roller 24 and four sealing rollers 25 which are electrically heated and spaced apart from one another.
A dosing unit 26 to feed a dose of product 5 into each tube between the semirigid plastic material strip 15 and the flexible plastic material strip 18 is arranged in the forming station 16 and at the longitudinal sealing device 23. The dosing unit 26 comprises three twin feeding ducts 27, each of which is vertically arranged between two sealing rollers 25 of the longitudinal sealing device 23 and feeds the doses of product 5 between the semirigid plastic material strip 15 and the flexible plastic material strip 18.
Finally, the forming station 16 comprises a transversal roller sealing device 28, which is arranged downstream of the longitudinal sealing device 23 and transversely seals together the two strips 15 and 18 in order to define a series of pockets 4 (shown in FIG. 1) along each tube, each of which contains a dose of product 5. According to a preferred embodiment, the transversal sealing device 28 comprises a contrast roller 29 and a sealing roller 30, which is electrically heated and cooperates with the contrast roller 29.
Finally, a cutting device 31 is arranged downstream of the forming station 16 so as to cut transversely the strips 15 and 18 arranged one on top of the other and sealed so as to separate in sequence the sealed single-dose packages 1. An outlet conveyor belt 32 is arranged under the cutting device 31, on which the sealed single-dose packages 1 fall by gravity once they have been separated from the strips 15 and 18 arranged on top of and sealed to each other.
The flexible plastic material strip 18 is normally pre-printed, whereas, as previously said, the semirigid plastic material strip 15 is printed inside the packaging machine 11 by using the printing unit 19; according to an alternative embodiment, the printing unit 19 is not present (or is disabled), therefore the semirigid plastic material strip 15 is also pre-printed (or without prints). The flexible plastic material strips 15 and/or 18 are generally provided with reference notches, which are read by special optical sensors to synchronize the several operations appropriately, so that the printed zones are correctly centered in the finished sealed single-dose packages 1. The reference notches are preferably printed in the zones of strips 15 and/or 18 which are discarded by the cutting device 31 so as not to be present in the finished sealed single-dose packages 1.
As shown in FIG. 9, the printing unit 19 of the semirigid plastic material strip 15 comprises a conveying device 33 (diagrammatically shown) which feeds the semirigid plastic material strip 15 along a (substantially vertical) conveying direction C, and a printing device 34 arranged in a fixed position along the conveying device 33 and facing the outer surface 10 of the semirigid plastic material strip 15 so as to print a pattern on the strip 15 itself. The printing device 34 is a heat transfer printing device and comprises a printing head 35, which is movable perpendicularly to the conveying direction C along a printing direction S so as to contact the semirigid plastic material strip 15; in other words, in use, the printing head 35 is movable along the printing direction S, which is orthogonal to the conveying direction C and orthogonal to the semirigid plastic material strip 15 so as to come into contact with the outer surface 10 of the semirigid plastic material strip 15. Therefore, in use, the printing head 35 contacts the semirigid plastic material strip 15 with a given pressure so as to print a pattern on the semirigid plastic material strip 15.
The printing device 34 further comprises a fixed contrast plate 36 (i.e. in a fixed position), which is independent and separate from the conveying device 33, is arranged in a fixed position along the conveying device 33, and is arranged parallel to and facing the printing device 34 so that the semirigid plastic material strip 15 is arranged between the contrast plate 36 and the printing device 34. When the printing head 35 moves towards the semirigid plastic material strip 15, the printing head 35 presses the semirigid plastic material strip 15 against the contrast plate 36 and therefore the printing head 35 may exert a given pressure on the outer surface 10 of the semirigid plastic material strip 15, which pressure is required to carry out the printing process properly.
The contrast plate 36 comprises a plurality of nozzles 37, each of which opens up onto the semirigid plastic material strip 15 and is adapted to release a compressed air blow. In particular, each nozzle 37 consists of a through hole, which is obtained through the contrast plate 36 and receives the compressed air by means of a pipe 39 connected to a compressed air source 40. The compressed air blown by the nozzles 37 creates a pressurized air cushion 38 at the inner surface 8 of the semirigid plastic material strip 15, which inner surface 8 is opposite to the outer surface 10 and thus opposite to the printing device 34. The air cushion 38 thus made creates a deformable contrast which allows the printing head 35 to create a constant and even pressure against the outer surface 10 of the semirigid plastic material strip 15; in other words, the air cushion 38 is deformed in a variable and dynamic manner so as to adapt perfectly to the shape of the printing head 35, thus ensuring a completely even contact between the printing head 35 and the outer surface 10 of the semirigid plastic material strip 15. In summary, the contrast plate 36 comprises a plurality of nozzles 37, which open up onto the inner surface 8 of the semirigid plastic material strip 15 and are adapted to release a compressed air blow to create the pressurized air cushion 38 at the inner surface 8 of the semirigid plastic material strip 15, opposite to the printing device 34; the air cushion 38 forms a deformable contrast against which the printing head 35 pushes the semirigid plastic material strip 15. Thereby, the printing head 35 may operate under the most favorable conditions allowing a high quality pattern to be obtained in very short times (i.e. also when the packaging machine 11 operates at high speed).
According to a preferred embodiment, in order to maximize the effectiveness of the contrasting action of the air cushion 38, the compressed air is fed to the nozzles 37 with a pressure from 2 to 6 bar (preferably from 3 to 5 bar).
According to an alternative embodiment (not shown), the printing device 34 may use a printing technology other than heat transfer (e.g. it might use ink-jet); in this case, the printing head 35 is fixed (i.e. does not translate perpendicularly to the semirigid plastic material strip 15).
As shown in FIG. 4, the incision unit 20 cooperates with the conveying device 21 which feeds the semirigid plastic material strip 15 along the conveying direction C. The incision unit 20 comprises two support plates 41, which are arranged along the conveying device 21 downstream of the feeding dandy rollers 22 so that the feeding dandy rollers 22 cyclically allow the semirigid plastic material strip 15 to temporarily stop between the two support plates 41. The two support plates 41 are arranged on opposite sides of the semirigid plastic material strip 15; therefore, each support plate 41 faces a corresponding surface 8 or 10 of the semirigid plastic material strip 15.
As shown in FIGS. 5-8, the incision unit 20 is provided with six incision devices 42, each of which cuts an incision 7 or 9 (shown in FIG. 3) into a corresponding surface 8 or 10 of the semirigid plastic material strip 15; in particular, three incision devices 42 a, which are arranged one next to the other, cut respective inner incisions 7 into the inner surface 8 of the semirigid plastic material strip 15 and three incision devices 42 b, which are arranged one next to the other, cut respective outer incisions 9 into the outer surface 10 of the semirigid plastic material strip 15. Each incision device 42 comprises a cutting element 43 supported by a support plate 41 and facing the corresponding surface 7 or 9 of the semirigid plastic material strip 15, and a contrasting element 44 supported by the other support plate 41 and facing the corresponding surface 9 or 7 of the semirigid plastic material strip 15. Each cutting element 43 is provided with a blade (not shown in detail) which is preferably V-shaped; in contrast, each contrast element 44 is flat so as to provide the blade of the corresponding cutting element 43 with an even contrast.
The two support plates 41 are mechanically connected together so as to move synchronously along a translation direction T which is orthogonal to the conveying direction C; in particular, the two support plates 41 are mounted so as to be movable on corresponding rails 45 so as to translate (slide) together along the translation direction T, which is orthogonal to the conveying direction C. In other words, the two support plates 41 are provided with corresponding slides, which are slidingly coupled to the rails 45 so as to translate (slide) along the translation direction T under the control of an actuating device 46 (e.g. of the electric or pneumatic type). The six incision devices 42 are arranged one next to the other and are aligned along the translation direction T. The actuating device 46 cyclically moves the two support plates 41 forward and backward along the translation direction T between a first position (shown in FIGS. 5 and 6), in which the incision devices 41 a cut the inner incisions 7 into the inner surface 8 of the semirigid plastic material strip 15, and a second position (shown in FIGS. 7 and 8), in which the incision devices 41 b cut the outer incisions 9 into the outer surface 10 of the semirigid plastic material strip 15.
Each support plate 41 supports the cutting elements 43 of an incision device 42 a or 42 b and the contrast elements 44 of the other incision device 42 b or 42 a; in other words, each support plate 41 supports both three cutting elements 43 and three contrast elements 44.
A support plate 41 is movably mounted on corresponding rails 47 so as to translate (slide) cyclically forward and backward towards the other support plate 41 and along an incision direction I, which is orthogonal to both the conveying direction C and the translation direction T. In other words, a support plate 41 is provided with corresponding slides which are slidingly coupled to the rails 47 so as to translate (slide) along the incision direction I under the control of an actuating device 48 (e.g. of the electric or pneumatic type).
In a preferred embodiment shown in the accompanying figures, each incision device 42 comprises an adjusting organ 49 (e.g. a micrometer) to adjust the depth of incision 7 or 9 by varying the relative position between the corresponding cutting element 43 or the corresponding contrast element 44 and the respective support plate 41. Each adjusting organ 49 is coupled to the cutting element 43 or to the contrast element 44 of the same incision device 42 and is adapted to adjust the distance between the cutting element 43 or the contrast element 44 and the semirigid plastic material strip 15.
In a preferred embodiment shown in the accompanying figures, the adjusting organs 49 are all arranged on the same support plate 41 so as to facilitate the access by an operator to the adjusting organs 49; in other words, if all the adjusting organs 49 are arranged on the same support plate 41, it is sufficient to allow an operator to access said support plate 41 in order to act on all the adjusting organs 49.
The operation of the incision unit 20 is described below with reference to FIGS. 5-8.
Firstly, the semirigid plastic material strip 15 is arranged at the incision devices 42 a (FIG. 5), i.e. is arranged between the incision devices 42 a. At this point and as shown in FIG. 6, the two support plates 41 are approached each other by operating actuator 48, which translates a support plate 41 along the rails 47 and in the incision direction I; such a relative movement between the two support plates 41 leads the incision devices 42 a to cut the inner surface 8 of the semirigid plastic material strip 15 (by approaching together the corresponding cutting elements 43 and contrast elements 44) so as to cut the inner incisions 7 (the incision devices 42 b also perform an incision movement, although without practical effects since the semirigid plastic material strip 15 is not present between the incision devices 42 b).
Once the cutting of the inner incisions 7 into the inner surface 8 of the semirigid plastic material strip 15 has been completed, the support plates 41 are brought back to their initial distance (FIG. 5); the two support plates 41 are then translated together by operating actuator 46 so as to move the two support plates 41 laterally in the translation direction T in order to invert the incision devices 42 coupled to the semirigid plastic material strip 15. In other words, firstly the incision devices 42 a are coupled to the semirigid plastic material strip 15 (FIG. 5), whereas at the end of the lateral translation of the two support plates 41, the incision devices 42 b are coupled to the semirigid plastic material strip 15 (FIG. 7).
At this point and as shown in FIG. 8, the two support plates 41 are approached each other by operating actuator 48, which translates a support plate 41 along the rails 47 and in the incision direction I; such a relative movement between the two support plates 41 leads the incision devices 42 b to cut the outer surface 10 of the semirigid plastic material strip 15 (by approaching together the corresponding cutting elements 43 and contrast elements 44) so as to cut the outer incisions 9 (the incision devices 42 a also perform an incision movement, although without practical effects since the semirigid plastic material strip 15 is not present between the incision devices 42 a).
Once the cutting of the outer incisions 9 into the outer surface 10 of the semirigid plastic material strip 15 has been completed, the cycle of the incision unit 20 is completed and the semirigid plastic material strip 15 is fed from the conveying device 21 along the conveying direction C.
The semi rigid plastic material strip 15 does not move (i.e. is stationary in the same position) between the cutting of the inner incisions 7 into the inner surface 8 of the semirigid plastic material strip 15 and the cutting of the outer incisions 9 into the outer surface 10 of the semirigid plastic material strip 15, since the incision devices 42 supported by the two support plates 41 perform a lateral translation; thereby, the incisions 7 and 9 have an almost perfect alignment with respect to each other since it is totally free from possible errors due to the incorrect positioning of the semirigid plastic material strip 15.
As shown in FIG. 10, the dosing unit 26 comprises a tank 50 holding the fluid product 5 and three feeding ducts 27, each of which originating from tank 50 and ending with a delivery mouth 51 which is arranged at the longitudinal sealing device 23. A pump 52 is arranged along each feeding duct 27 so as to feed the fluid product 5 from tank 50 towards the delivery mouth 51.
Each pump 52 is a volumetric pump of peristaltic type (i.e. is a peristaltic pump) so as to provide for a precise dosing of product 5. According to a preferred embodiment, each peristaltic pump 52 has an impeller which supports a plurality of thrust elements (not less than four thrust elements and preferably eight thrust elements).
According to a preferred embodiment, tank 50 is pressurized at a pressure which is higher than the atmospheric pressure; such a feature allows the suction of product 5 by the peristaltic pumps 52 to be enhanced thus avoiding the occurrence of “voids” along the feeding ducts 27 and increasing the precision of dosing product 5. In particular, tank 50 has at least one nozzle 53, which is arranged in an upper portion of tank 50 and is adapted to blow a compressed air jet into tank 50, which keeps the internal volume of tank 50 under pressure (i.e. pressurized).
According to a preferred embodiment, a shutoff valve 54 is included, which is arranged along each feeding duct 27 upstream of the corresponding peristaltic pump 52. The shutoff valves 54 allow the flow of product 5 along the feeding ducts 27 to be stopped when the packaging machine 11 is stopped (with the packaging machine 11 stopped and in the absence of the shutoff valves 54, a small amount of product 5 would continue to flow by gravity along the feeding ducts 27).
The dosing unit 26 allows the fluid product 5 (in particular a sanitizing gel) to be dosed with high precision (of the order of ±2-3%) even in the case of very small amounts (e.g. of the order of one millimeter of fluid product in each single-dose package 1). Such a result is also achieved, inter alia, by using peristaltic pumps 52 which maintain a high precision even in the case of low volumetric capacity.
The above-described packaging machine 11 has three production lines arranged one next to the other and operating in parallel; a different number of production lines can obviously be provided as a function of the throughput required (e.g. a single production line or two, four or more production lines).
In known packaging machines, dosing very small doses of fluid product (of the order of one millimeter of fluid product in each single-dose package) might result in a relatively low precision (with an error of the order of ±6-8%). To solve this problem, a dosing unit 26 may be used, comprising: a tank 50 holding a fluid product 5; at least one feeding duct 27, which originates from tank 50 and ends with a delivery mouth 51; and a peristaltic pump 52 which is arranged along the feeding duct 27 so as to feed the fluid product 5 from tank 50 to the delivery mouth 51, where tank 50 is pressurized at a pressure which is higher than the atmospheric pressure.
Preferably, tank 50 has at least one nozzle 53, which is arranged in an upper portion of tank 50 and is adapted to blow a compressed air jet into tank 50. Preferably, the peristaltic pump 52 has an impeller which supports at least four thrust elements. Preferably, the peristaltic pump 52 has an impeller which supports eight thrust elements. A shutoff valve 54 is preferably provided, which is arranged along the feeding duct 27 upstream of pump 52.
In known packaging machines, it has been noted that, when operating at high speed, the pattern of the semirigid plastic material strip has not always an optimal quality. In particular, the pattern might be incomplete, i.e. have some larger or smaller zones with no printing, due to a non-optimal contact between a printing head of a printing device and the semirigid plastic material strip during the printing process. In order to improve the contact between the printing head and the semirigid plastic material strip, it has been suggested to decrease the distance between the printing device and a fixed contrast opposed to the printing device so as to increase the pressure with which the printing head pushes the semirigid plastic material strip against the contrast; however, such a solution might determine the occurrence of an excessive mechanical stress on the printing head, which stress might lead in a short time to breakage of the printing head. In order to solve this problem, a printing unit 19 may be used, comprising: a conveying device 33, which feeds strip 15 along a conveying direction C; a printing device 34 facing a first surface 10 of strip 15 so as to print a pattern on strip 15; and a contrast plate 36, which is parallel to and faces the printing device 34 so that strip 15 is arranged between the contrast plate 36 and the printing device 34, where the contrast plate 36 comprises at least one nozzle 37, which opens up onto a second surface 8 of strip 15 and is adapted to release a compressed air blow. The compressed air blown by nozzle 37 preferably creates a pressurized air cushion 38 at the second surface 8 of strip 15 opposite to the printing device 34. The contrast plate 36 preferably comprises a plurality of nozzles 37 spaced apart from one another. Preferably, the printing device 34 is a heat transfer printing device. The printing device 34 preferably comprises a printing head 35 which is movable along a printing direction S orthogonal to the conveying direction C and orthogonal to strip 15. The compressed air is preferably fed to nozzle 37 with a pressure from 2 to 6 bar. The compressed air is preferably fed to nozzle 37 with a pressure from 3 to 5 bar.

Claims

1. A unit for the incision of a strip made of a plastic material to cut two distinct incisions into two opposite surfaces of the strip in a packaging machine to manufacture a sealed single-dose break-open package; the incision unit comprises:

a conveying device, which feeds the strip along a conveying direction;

two support plates, which are arranged on opposite sides of the strip, so that each support plate faces a corresponding surface of the strip; and

at least two incision devices, each of which cuts an incision into a corresponding surface of the strip and comprises a cutting element, which is supported by a support plate, and a contrast element, which is supported by the other support plate;

wherein the two support plates are mobile so as to translate together along a translation direction, which is orthogonal to the conveying direction;

wherein the two incision devices are arranged one next to the other and are aligned along the translation direction; and

wherein a first actuating device is provided, which cyclically moves the two support plates forward and backward along the translation direction between a first position, in which a first incision device is operated so as to cut a first incision, and a second position, in which a second incision device is operated so as to cut a second incision, which is opposite to the first incision.

2. An incision unit according to claim 1, wherein each support plate supports the cutting element of an incision device and the contrast element of the other incision device.

3. An incision unit according to claim 1, wherein each cutting element comprises a blade.

4. An incision unit according to claim 3, wherein each blade is V-shaped and each contrast element is flat.

5. An incision unit according to claim 1, wherein each incision device comprises an adjusting organ, which is coupled to the cutting element or to the contrast element and adjusts the distance between the cutting element or the contrast element and the strip.

6. An incision unit according to claim 5, wherein the adjusting organs are all arranged on a same support plate.

7. An incision unit according to claim 1, wherein at least one support plate is mobile so as to cyclically move forward and backward, due to a second actuating device, towards the other support late and along an incision direction, which is perpendicular to the strip and perpendicular to both the conveying direction and the translation direction.

8. An incision unit according to claim 1, wherein the conveying device comprises at least one feeding dandy roller, which is arranged upstream of the support plates and is mobile so as to allow the strip to temporarily stop between the two support plates.

9. A packaging machine to manufacture a sealed single-dose break-open package;

the package consists of a first sheet made of a semirigid plastic material, which is arranged on top of and sealed to a second sheet made of a flexible plastic material, so as to define a sealed pocket containing a dose of a product, and has a pair of incisions to guide a controlled breaking of the first sheet;

the packaging machine comprises:

a first unwinding device to feed a first strip made of a semirigid plastic material;

a second unwinding device to feed a second strip made of a flexible plastic material;

an incision unit to cut two incisions into the first strip made of a semirigid plastic material;

a forming station, which is arranged downstream of the incision unit so as to arrange the first strip made of a semirigid plastic material on top of the second strip made of a flexible plastic material;

a first longitudinal sealing device to longitudinally and laterally seal the two strips to one another, so as to define at least one tube;

a dosing unit, which is arranged in the forming station so as to feed a dose of a product into the tube between the first strip made of a semirigid plastic material and the second strip made of a flexible plastic material;

a second transverse sealing device, which is arranged downstream of the dosing device so as to transversely seal the two strips to one another in order to define, along the tube, a series of pockets, each containing a dose of product; and

a cutting device, which is arranged downstream of the forming station so as to transversely cut the tube in order to separate, in sequence, the sealed single-dose packages (1);

wherein the incision unit is manufactured according to claim 1.

10. A method for the incision of a strip made of a plastic material to cut two distinct incisions into two opposite surfaces of the strip in a packaging machine to manufacture a sealed single-dose break-open package; the incision method comprises the steps of:

conveying the strip along a conveying direction and between two support plates, so that each support plate faces a corresponding surface of the strip;

cutting the strip by means of at least two incision devices, each cutting an incision into a corresponding surface of the strip;

translating the two support plates together along a translation direction, which is orthogonal to the conveying direction; and

cyclically moving the two support plates forward and backward along the translation direction between a first position, in which a first incision device is operated so as to cut a first incision, and a second position, in which a second incision device is operated so as to cut a second incision, which is opposite to the first incision.

11. A method for the incision of a strip made of a semirigid material according to claim 10, wherein the two incision devices are arranged one next to the other and are aligned along the translation direction.

12. A method for the incision of a strip made of a semirigid material according to claim 10, wherein the strip made of a semirigid material is temporarily stopped during the strip incision step.

13. A dosing unit of a packaging machine for sealed single-dose packages; the dosing unit comprises:

a tank holding a fluid product;

at least one feeding duct, which originates from the tank and ends with a delivery mouth; and

a pump, which is peristaltic pump and is arranged along the feeding duct so as to feed the fluid product from the tank to the delivery mouth;

wherein the tank is pressurized at a pressure that is higher than the atmospheric pressure.

14. A dosing unit according to claim 13, wherein the tank has at least one nozzle, which is arranged in an upper portion of the tank and is suited to blow a jet of compressed air into the tank.

15. A dosing unit according to claim 13, wherein the peristaltic pump has an impeller, which supports at least four thrust elements.

16. A dosing unit according to claim 13, wherein the peristaltic pump has an impeller, which supports at least eight thrust elements.

17. A dosing unit according to claim 13 and comprising a shut-off valve, which is arranged along the feeding duct upstream of the pump.

18. A dosing unit according claim 13, wherein the fluid product is a sanitizer gel.

19. A unit to print a deformable plastic material strip of a packaging machine for sealed single-dose packages; the printing unit comprises:

a conveying device, which feeds the strip along a conveying direction;

a printing device, which is arranged in a fixed position along the conveying device and faces a first surface of the strip so as to print a pattern on the strip; and

a contrast plate, which is independent and separate from the conveying device, is arranged in a fixed position along the conveying device, and is parallel to and faces the printing device so that the strip is arranged between the contrast plate and the printing device;

wherein the printing device comprises a printing head, which in use contacts the strip with a given pressure so as to print a pattern on the strip; and

wherein the contrast plate comprises at least one nozzle, which opens up onto a second surface of the strip and is suited to release a blow of compressed air so as to create a pressurized air cushion in correspondence to the second surface of the strip that is opposite to the printing device, said air cushion constitutes a deformable contrast against which the printing head pushes the strip.

20. A printing unit according to claim 19, wherein the contrast plate comprises a plurality of nozzles that are spaced apart from one another.

21. A printing unit according to claim 19, wherein the printing device is a heat transfer printing device.

22. A printing unit according claim 19, wherein the printing head is mobile along a printing direction, which is orthogonal to the conveying direction and orthogonal to the strip.

23. A printing unit according to claim 19, wherein the compressed air is fed to the nozzle with a pressure ranging from 2 to 6 bar.

24. A printing unit according to claim 19, wherein the compressed air is fed to the nozzle with a pressure ranging from 3 to 5 bar.

25. A method to print a deformable plastic material strip of a packaging machine for sealed single-dose packages; the printing method comprises the steps of:

conveying the strip along a conveying direction by means of a conveying device;

printing a first surface of the strip by means of a printing device, which is arranged in a fixed position along the conveying device and is coupled to a contrast plate, which is independent and separate from the conveying device, is arranged in a fixed position along the conveying device, and is parallel to and faces the printing device so that the strip is arranged between the contrast plate and the printing device; wherein the printing device comprises a printing head, which in use contacts the strip with a given pressure so as to print a pattern on the strip; and

releasing a blow of compressed air through a nozzle, which is obtained through the contrast plate and opens up onto a second surface of the strip so as to create a pressurized air cushion in correspondence to the second surface of the strip that is opposite to the printing device, said air cushion constitutes a deformable contrast against which the printing head pushes the strip.