Patent Description:
More precisely, the invention relates to a method for transverse cutting of a water-soluble tape.

Single-dose capsules are water-soluble sachets containing laundry or dishwasher detergents, fabric softeners or other products for household appliances. Single-dose capsules are becoming increasingly popular due to the ease of use for the user. Single-dose detergent capsules also have a positive impact on sustainability as they contain the precise dose of detergent for one load and are a way to reduce waste.

Single-dose capsules are generally produced by forming recesses in a first water-soluble film, filling the recesses with fluid or powder compositions, applying a second water-soluble film over the first water-soluble film, and binding the first and second water-soluble films together to seal the compositions between the two water-soluble films.

Machines for producing single-dose capsules generally form a water-soluble tape movable in a machine direction, comprising a plurality of single-dose capsules joined together by flat areas in which the first and second water-soluble films are joined in contact with each other. In the water-soluble tape, the single-dose capsules are arranged in a plurality of transverse rows and in a plurality of longitudinal rows. The water-soluble tape is then cut transversely and in a longitudinal direction along the flat areas to form individual single-dose capsules.

<CIT> discloses a method for cutting a water-soluble tape in the transverse direction, said tape being formed by transverse and longitudinal rows of single-dose capsules joined together. The transverse cut is carried out by a cutting unit comprising an anvil and a knife roller rotating around respective parallel axes. The water-soluble tape moves in a machine direction at a speed V1, and is passed between the anvil and the knife roller. Advantageously, the speed V1 may be constant.

The knife roller comprises one or more blades and rotates at a variable speed. When cutting the water-soluble tape, the knife roller blades move at the same speed as the water-soluble tape.

The cutting of the water-soluble film by means of a knife roller equipped with blades that act on an anvil requires mechanical interference between the blades and the anvil. The interference value necessary for the system to be able to cut the water-soluble film depends on many factors, linked both to the properties of the material to be cut and to the cutting technology used. The interference between the blades and the anvil generates mechanical stresses, so that it would be desirable to reduce the degree of interference as much as possible, without however affecting the ability to effectively make the cut.

The cutting units, to reduce to a minimum the interference values, must be made with particular constructive attention in terms of precision and stiffness. A high construction accuracy may reduce but hardly eliminate alignment errors, concentricity, or defects of the knife blades, which require greater interference and cutting forces to be compensated for.

The object of the present invention is to provide a method for transverse cutting of a water-soluble tape that overcomes the problems of the prior art.

According to the present invention, this object is achieved by a method having the characteristics of claim <NUM>.

Optional characteristics of the invention form the subject of the dependent claims.

The claims form an integral part of the disclosure provided here in relation to the invention.

Further characteristics and advantages of the invention will become clear from the detailed description that follows, given purely by way of nonlimiting example, with reference to the attached drawings, in which:.

It will be appreciated that the accompanying drawings are schematic and that some components may not be for a better understanding of the figures. It will be appreciated that the various figures may also not be represented on the same scale.

With reference to <FIG>, a machine for producing single-dose capsules is indicated by the reference number <NUM>.

The machine <NUM> comprises a forming surface <NUM> having a plurality of cavities <NUM>, continuously movable in a machine direction MD. In the embodiment shown in <FIG>, the forming surface <NUM> is the outer cylindrical surface of a wheel <NUM> rotating about a horizontal axis A. In a possible embodiment, the forming surface <NUM> may be the outer surface of a closed-loop belt.

The machine <NUM> comprises a first feeding unit <NUM> configured to feed a first continuous water-soluble film <NUM> onto the forming surface <NUM>. The first continuous water-soluble film <NUM> is unwound from a first reel <NUM> and is fed to the forming surface <NUM> at a first position <NUM>.

The machine <NUM> may comprise a heating device <NUM> arranged to heat the first continuous water-soluble film <NUM> upstream of the forming surface <NUM>. The heating device <NUM> may comprise a heated roller <NUM>, which is in contact with the first continuous water-soluble film <NUM> upstream of the first position <NUM>.

The first continuous water-soluble film <NUM> is retained on the forming surface <NUM> while moving in the machine direction MD. The first continuous water-soluble film <NUM> may be retained on the forming surface <NUM> by mechanical retaining elements, which act on the lateral edges of the first continuous water-soluble film <NUM>, for example, by belts which hold the lateral edges of the first continuous water-soluble film <NUM> on the outer surface of the wheel <NUM>.

The first continuous water-soluble film <NUM> deforms in the cavities <NUM> of the forming surface <NUM> while moving in the machine direction MD. The deformation of the first continuous water-soluble film <NUM> at the cavities <NUM> may be obtained by a suction system comprising a plurality of holes opened on the surfaces of the cavities <NUM> and fluidly connected to a stationary suction chamber connected to a subatmospheric pressure source. The first continuous water-soluble film <NUM> is kept adherent to the walls of the cavities <NUM> by said suction system, so that a plurality of recesses are formed in the first continuous water-soluble film <NUM>, having the same shape as the cavities <NUM>.

The machine <NUM> comprises a second feeding unit <NUM> configured to feed a second continuous water-soluble film <NUM> onto the forming surface <NUM> at a second position <NUM> located downstream of the first position <NUM> with respect to the machine direction MD. The second continuous water-soluble film <NUM> is unwound from a second reel <NUM>.

The machine <NUM> comprises a dosing apparatus <NUM> configured to dispense metered quantities of at least one composition into the recesses of the first continuous water-soluble film <NUM>, which are arranged at the cavities <NUM> of the forming surface <NUM>. The dosing apparatus <NUM> is arranged in an intermediate position between the first position <NUM> and the second position <NUM>. The dosing apparatus <NUM> fills the recesses of the first continuous water-soluble film <NUM> with one or more compositions. After the recesses of the first continuous water-soluble film <NUM> have been filled with the compositions, the second continuous water-soluble film <NUM> is applied onto the first continuous water-soluble film <NUM>, so as to enclose the metered amounts of compositions contained in the recesses between the first and the second continuous water-soluble film <NUM>, <NUM>.

The machine <NUM> comprises a wetting unit <NUM> configured to wet a surface of the second continuous water-soluble film <NUM> upstream of the second position <NUM>. The wetting unit <NUM> comprises a wetting roller <NUM> that is in contact with the surface of the second continuous water-soluble film <NUM>, which will be placed in contact with the first continuous water-soluble film <NUM>.

The machine <NUM> may comprise a pressure roller <NUM> configured to press the first and second continuous water-soluble films <NUM>, <NUM> against the forming surface <NUM> in the contact areas surrounding the cavities <NUM> containing the metered compositions. The first and second continuous water-soluble films <NUM>, <NUM> are waterbonded to each other at respective contact areas surrounding the recesses containing the metered compositions.

With reference to <FIG>, after the reciprocal bonding between the first and second continuous water-soluble films <NUM>, <NUM>, a water-soluble tape <NUM> is formed. Within the water-soluble tape <NUM>, single-dose capsules <NUM> are formed, connected and separated from each other by flat areas <NUM>, <NUM> comprising a first side <NUM> and a second side <NUM>.

The single-dose capsules <NUM> are arranged in transverse rows <NUM> and longitudinal rows <NUM>. The single-dose capsules <NUM> of the transverse rows <NUM> are joined together by transverse flat areas <NUM>, and the single-dose capsules <NUM> of the longitudinal rows <NUM> are joined together by longitudinal flat areas <NUM>. In the flat areas <NUM>, <NUM>, the first and second continuous water-soluble films <NUM>, <NUM> are joined in contact with each other.

The flat areas <NUM>, <NUM> may have a thickness of between <NUM> microns and <NUM> microns.

In a possible embodiment, the single-dose capsules <NUM> protrude outwards from the first side <NUM>, i.e. from the side of the first water-soluble film <NUM>.

In a possible embodiment, the single-dose capsules <NUM> protrude outwards from the second side <NUM>, i.e. from the side of the second water-soluble film <NUM>.

The machine <NUM> comprises a longitudinal cutting unit <NUM> and a transverse cutting unit <NUM>, which cut the water-soluble tape <NUM> along the longitudinal flat areas <NUM>, and along the transverse flat areas <NUM>, so as to form individual single-dose capsules <NUM>.

In the embodiment illustrated in <FIG>, the longitudinal cutting unit <NUM> is arranged upstream of the transverse cutting unit <NUM> with reference to the machine direction MD. In this embodiment, the longitudinal cutting unit <NUM> may comprise a plurality of discs <NUM> cooperating with the forming surface <NUM> and arranged to cut the water-soluble tape <NUM> along the longitudinal flat areas <NUM>.

With reference to <FIG> and <FIG>, the transverse cutting unit <NUM> comprises an anvil <NUM> and a knife roller <NUM>, rotating around respective rotation axes A and B, parallel to each other and perpendicular to the machine direction MD. The water-soluble tape <NUM> passes between the anvil <NUM> and the knife roller <NUM>. The knife roller <NUM> cuts the water-soluble tape <NUM> along the transverse flat areas <NUM>.

With reference to <FIG>, the machine <NUM> may comprise an inlet transfer roller <NUM>, which transfers the water-soluble tape <NUM> from the forming surface <NUM> to the anvil <NUM>, and an outlet transfer roller <NUM>, which receives the individual single-doses capsules <NUM> from the anvil <NUM> and transfers them to an outlet conveyor <NUM>.

In a possible embodiment (not shown) the longitudinal cutting unit <NUM> may be arranged downstream of the transverse cutting unit <NUM> with reference to the machine direction MD, so that the cutting of the transverse flat areas <NUM> is carried out before the cutting of the longitudinal flat areas <NUM>.

With reference to <FIG>, the knife roller <NUM> comprises one or more knives <NUM> mounted on the rotating knife roller <NUM> and having respective cutting edges <NUM> movable along a circular path <NUM>. The number of knives <NUM> may vary from <NUM> to <NUM> according to the dimensions of the knife roller <NUM>. If several knives <NUM> are provided, the respective cutting edges <NUM> are spaced apart from each other in an angular direction by an equal distance.

The anvil <NUM> may have a plurality of seats <NUM> configured to receive respective single-dose capsules <NUM>. The seats <NUM> may be configured to retain the single-dose capsules <NUM>, for example, by suction. The anvil <NUM> may have a plurality of contrast elements <NUM> that cooperate with the cutting edges <NUM> of the knives <NUM> to cut the transverse flat areas <NUM> of the water-soluble tape <NUM>. The contrast elements <NUM> are arranged between two transverse rows of seats <NUM> adjacent to each other.

The anvil <NUM> and the knife roller <NUM> are driven in rotation around the respective rotation axes A and B by respective electric motors <NUM>, <NUM> controlled by a control unit <NUM>.

With reference to <FIG>, the control unit <NUM> rotates the anvil <NUM> with a peripheral speed V1 equal to the feed rate of the water-soluble tape <NUM> in the machine direction MD. The peripheral speed V1 of the anvil <NUM> is the linear speed of the outer surfaces <NUM> of the contrast elements <NUM>, which is equal to the angular velocity W1 of the anvil <NUM> multiplied by the radial distance R1 between the outer surfaces <NUM> of the contrast elements <NUM> and the rotation axis A of the anvil <NUM>.

The control unit <NUM> rotates the knife roller <NUM> with a variable peripheral speed V2 along the trajectory <NUM>. The peripheral speed V2 of the knife roller <NUM> is the linear speed of the cutting edges <NUM> of the knives <NUM>, which is equal to the angular speed W2 of the knife roller <NUM> multiplied by the radial distance R2 between the cutting edges <NUM> of the knives <NUM> and the rotation axis B of the knife roller <NUM>.

During a single cutting cycle, the rotating knife roller <NUM> rotates with at least one first peripheral speed V2' and with a second peripheral speed V2".

The first peripheral speed V2' is greater than the peripheral speed V1 of the anvil <NUM>. The second peripheral speed V2" is at least <NUM>% faster than the first peripheral speed V2'.

The rotating knife roller <NUM> rotates at the speed V2' when each individual knife <NUM> cuts the water-soluble tape <NUM> in a direction transverse to the machine direction MD.

In one complete rotation of the rotating knife roller <NUM>, a number of cutting cycles equal to the number of knives <NUM> on the rotating knife roller <NUM> are performed. Each cut of the water-soluble tape <NUM> is carried out only one at a time by the knives <NUM>.

In the instants wherein the cutting edge <NUM> of a knife <NUM> comes into contact with a respective contrast element <NUM> of the anvil <NUM>, the peripheral speed V2' of the knife roller <NUM> is greater than the peripheral speed V1 of the anvil <NUM>.

In the instants wherein the cutting edge <NUM> of a knife <NUM> comes into contact with a respective contrast element <NUM> of the anvil <NUM>, the ratio V2'/V1 is between <NUM> and <NUM>. In a possible embodiment, the speed ratio V2'/V1 is between <NUM> and <NUM>.

It is advantageous that the speed ratio V2'/V1 does not drop to the value <NUM> because - in this way - it is not necessary to slow down the knife roller <NUM> to the peripheral speed V1 and then accelerate it again.

It is also advantageous to avoid the speed ratio V2'/V1 from exceeding <NUM> to avoid risks of incomplete cuts, breakage of the capsules, snags in the line, and malformations of the cutting profile along the flat areas.

In a possible embodiment, the ratio between the first peripheral speed V2' and the speed V1 is between <NUM> and <NUM>. In this range, there are no incomplete cuts, broken capsules, snags in the line or malformations of the cutting profile along the flat areas. Compared to the wider range, in this case, the risks of malfunctions are absent, while with the wider range malfunctions are possible, although with a very low probability (about <NUM>%).

After having performed a cut, the peripheral speed V2 of the knife roller <NUM> increases to the value V2" to align the knife <NUM>, or a subsequent knife <NUM>, with the successive contrast element <NUM> in a subsequent cutting step.

The graphs of <FIG>show the variation of the ratio V2/V1 during a complete rotation of the knife roller <NUM>. <FIG> refers to a knife roller <NUM> having four knives <NUM> and <FIG> refers to a knife roller <NUM> having six knives <NUM>. The areas of the graphs wherein the V2/V1 ratio is minimum (equal to approximately <NUM>) are the instants wherein the transverse cuts of the water-soluble tape <NUM> take place.

The difference between the peripheral speed V2' of the cutting edge <NUM> of the knife roller <NUM> and the peripheral speed of the anvil <NUM> during the cutting of the water-soluble tape <NUM> causes the point of contact between the cutting edge <NUM> and the anvil <NUM> to move between the instant of starting the cut and the instant of ending the cut. Since, during the cutting step, the peripheral speed V2' of the knife roller <NUM> is higher than the peripheral speed V1 of the anvil <NUM>, the knife roller <NUM> disengages from the anvil <NUM> into a more advanced relative position than the relative position in which it was engaged. This relative displacement creates a detachment and a consequent spacing apart between the two cut edges of the first and second water-soluble films <NUM>, <NUM>.

The fact that during cutting a distance is formed between the cut edges of the water-soluble films <NUM>, <NUM> allows reduction of the compressive force and the interference with which the cut edges <NUM> are pressed against the respective contrast elements <NUM>. This leads to a consequent reduction in the stresses to which the cutting system is subjected (blades, shafts, bearings and motors).

The higher peripheral speed of the knife roller <NUM> with respect to that of the anvil <NUM>, other conditions being equal, also reduces the contact time between the cutting edge <NUM> and the anvil <NUM>.

Claim 1:
A method for cutting a water-soluble tape (<NUM>) comprising the steps of:
- providing an anvil (<NUM>),
- providing a rotating knife roller (<NUM>) comprising at least one knife (<NUM>) having a cutting edge (<NUM>) extending outwards from said rotating knife roller (<NUM>),
- providing a water-soluble tape (<NUM>) comprising flat areas (<NUM>, <NUM>) comprising a first side (<NUM>) and a second side (<NUM>), and single-dose capsules (<NUM>) formed inside the water-soluble tape (<NUM>), wherein the single-dose capsules (<NUM>) are connected and separated from each other by the flat areas (<NUM>, <NUM>),
- advancing said water-soluble tape (<NUM>) in a machine direction (MD) at a speed (V1) between said anvil (<NUM>) and said rotating knife roller (<NUM>) with said first side (<NUM>) of the water-soluble tape (<NUM>) in contact with the anvil (<NUM>),
- cutting said water-soluble tape (<NUM>) with said at least one knife (<NUM>) while said water-soluble tape (<NUM>) passes between said anvil (<NUM>) and said rotating knife roller (<NUM>), wherein, during a single cutting cycle, the rotating knife roller (<NUM>) rotates with at least one first peripheral speed (V2') and a second peripheral speed (V2"), wherein the second peripheral speed (V2") is at least <NUM>% faster than the first peripheral speed (V2') and wherein the rotating knife roller (<NUM>) rotates at the first peripheral speed (V2') when a knife (<NUM>) cuts said water-soluble tape (<NUM>) in a direction transverse to the machine direction (MD),
wherein said method is characterized in that the ratio between the first peripheral speed (V2') and the speed (V1) is comprised between <NUM> and <NUM>.