Patent Application
20190134841
The present invention relates to a counter-die cylinder blanket of a die cutting machine which incorporates an insert to give rigidity to the blanket, being especially devised for rotating-type die cutting machines used in cardboard processing for the manufacturing of packaging.
The invention has the object of the particular configuration of the insert, which guarantees its centred positioning in the blanket during the manufacturing process thereof, in addition to relating to the process for producing said blanket.
The rotating-type die cutting machines generally comprise a pair of cylinders among which is made to pass through a sheet of cardboard for its die cutting, one of the cylinders of the pair incorporating a plurality of blades designed to make cuts in the sheet of cardboard whilst the other cylinder acts as a base for the die cutting.
This cylinder which acts as a base, generally known as counter-die cylinder, is usually made in high-resistance materials such as steel and, so that during the die cutting process no deterioration occurs in the blades, a coating is usually incorporated, also referred to as blanket, of a relatively soft material, which is typically polyurethane.
The blanket is generally materialized in a thick band of constant thickness designed to surround the cylinder, i.e. to form a type of cylindrical bushing concentric to the counter-die cylinder, a blanket which may incorporate a key designed to fit in a key seat defined in the counter-die cylinder.
Blanket bands are generally manufactured by means of filling by casting of a plastic material in fluid state at high temperatures in moulds of cylindrical geometry, with a key seat defined on the surface of the mould, to generate the key of the resulting band which, in this case constitutes the main fixing element of the band with the counter-die cylinder.
Solutions are known wherein the key of the band incorporates an insert which provides properties different or complementary to those of the material with which the band is manufactured, such as increasing rigidity of the key, improving quality of the closure of facilitating the assembly and dismantling procedure.
Said insert generally has an elongated geometry and may be subject to warping or torsions, both before being introduced in the key seat of the mould and on reaching certain temperatures during the band manufacturing process.
On the other hand, if it is desired that the insert is embedded in the band material during the hot pouring process thereof, it will be necessary for a certain clearance to be present with respect to the key seat wherein it is inserted, so that there is the risk that it displaces within said key seat, so that the final position in the blanket is not the desired one.
Finally, the introduction phase of the insert in the key seat during the manufacturing process of the blanket is especially critical if one wants a complete bond between the inset and the material of the band or key which surrounds it during filling. The walls of the key seat of the mould are typically impregnated, before the moulding operation, with a demoulding agent in order to facilitate the extraction of the band from the mould once the curing process of the poured plastic mass has finished.
In the event that the insert is not introduced centred in the mould key seat, it could establish direct contact with the walls of the key seat and, therefore, with the demoulding agent, and a correct adhesion would be produced of the insert in the key.
The object of the invention consists of a blanket designed to a counter-die cylinder comprising a band of plastic material of soft consistence, preferably polyurethane, which in turn has a key, obtained by means of moulding, and an insert of stiffening material of prismatic configuration housed in said key, which is formed by a body and a plurality of separating ribs which extend from the faces of the body.
The blanket is formed by moulding in a mould after the pouring of fluid plastic material and later curing, wherein the mould is formed by a cylindrical outer mould and a cylindrical inner mould provided with a key seat. The incorporation of the ribs in the insert facilitates their centring and separation with respect to the walls of the key seat of the inner mould, so that it avoids the aforementioned problems and drawbacks.
The incorporation of separating ribs will avoid that the main body of the insert is contaminated with the demoulding agent which will guarantee correct adhesion of the insert with the plastic material in liquid state during the moulding to produce the band.
The dimensions of the separating ribs defined on the faces of the stiffening insert are according to the separating distance that one wants to set between each one of the faces of the insert body and the walls of the mould key seat wherein it is designed to be housed.
The separating ribs are positioned uniformly throughout the surfaces of the insert body, preferably on those surfaces of the body parallel to the area of the mould key seat with the risk of presenting harmful agents for the adherence to the band during the filling of the mould, at a distance between them such that they guarantee the guiding parallel to a central shaft of said key seat of the mould from its insertion until its final position.
Likewise, said separating ribs have a round-tipped geometry which allows an easy sliding of the insert throughout the mould key seat, as well as its isolated contact during moulding. This geometry allows the adaptation to different dimensions of mould key seats maintaining an optimum adjustment, a continuous parallelism and final positioning. In this way, a first insert can be used in a predetermined range of width and depth of mould key seats.
It has also been preferably provided that the dimension of the body is in accordance with the mould key seat and that the separating ribs have the same height in order to guarantee the correct centring and positioning of the insert in the key seat of the mould.
In a first preferred embodiment, the insert comprises a plurality of upper and lower separators which emerge from the corresponding top and lower face of the body. This disposal makes it possible to overcome a series of problems, among which we can highlight the minimization of deficiencies in vulcanization, in those cases wherein a bond is desired between the insert and the rest of the band. Said deficiencies are usually mainly due to contamination by the demoulding agents impregnated in the mould key seat, which make contact with the insert body. On the other hand, it eliminates the torsions and warping by means of the guiding of the separators, guaranteeing that the polyurethane fixes the insert without their being trapping of air and the consequent bags.
In a second more preferred embodiment, the insert additionally comprises a plurality of side separators defined in its side faces.
To optimize contact and the bonding of the insert with the plastic material it is provided that the top face and/or the bottom face of said insert may incorporate grooves that extend longitudinally, preferably in the vicinity of the side faces, and the top face and/or the bottom face may have a rough surface, preferably a plurality of striations with geometry of saw tooth or undulating type, to increase adherence between the insert and the plastic material.
Additionally, and in the cases wherein one wants to guarantee good adhesion of the insert to the material poured on the mould once correctly positioned in the mould key seat, it is possible to previously perform several surface treatments on said insert, such as scoring, sandblasting, shot-blasting and/or gluing.
It is contemplated that, to facilitate the handling of the insert in the steps prior to its manual or automated introduction in the mould, said insert has additionally defined a handling area which enables the insertion in the key seat and, where relevant, guarantees the absence of undesired agents of the insert body in those cases wherein one wants a bond with the rest of the band material. This handling area may be removed in phases after the introduction, not forming part of the definitive piece.
On the other hand, it has been provided that the blanket may also incorporate a stiffening sheet, preferably fibre glass, which is normally separated by the upper ribs of the insert.
The manufacturing process of the blanket object of this invention uses a mould typically used in the mould-manufacturing of dollies formed by an inner mould provided with a key seat and an outer mould, concentric to the inner mould, between which a cavity is defined, wherein the blanket will be formed with the key.
The manufacturing process of the counter-die cylinder blanket of die cutting machine which is proposed in this invention incorporates, as a fundamental difference with respect to other processes, the step of introducing an insert of particular geometry, provided with separating ribs, which makes it possible to perform this introduction in a centred and guided form, parallel to the faces of the mould key seat as step prior to its filling with the manufacturing material of the blanket, which as has been indicated is preferably polyurethane in liquid state.
It also considers the possibility of introducing not only one but several inserts in the key seat, and which may be of any appropriate material.
To complement the description being made and in order to aid towards a better understanding of the characteristics of the invention, according to a preferred example of practical embodiment thereof, a set of drawings is attached as an integral part of said description wherein, with illustrative and non-limiting character, the following has been represented:
A detailed explanation is given below of examples of preferred embodiment of the object of the invention with the aid of the aforementioned figures.
The insert (5), shown in
The insert (5) incorporates in the top face (8) different grooves (12) which extend longitudinally between the front end (6) and the rear end (7), as observed, for example, in
It additionally contemplates that the insert (5) incorporates an extension or handling area (14) in its front end (6), as observed in
It is also provided that the band (3) additionally comprises a layer of stiffening material (15), as observed in
In the event one wants to form a blanket with a sheet of stiffening material (15), the manufacturing process starts with the positioning of said sheet of stiffening material (15) inside of the cavity (19) of the mould (16), adjacent to the surface of the inner mould (17).
Subsequently, the insert (5) is introduced in the mould key seat (20), by means of the use of the separating ribs (11) for an introduction and guiding parallel to the faces of the mould key seat (20), and to achieve a centred positioning of the insert (5) inside of said mould key seat (20).
In that moment the plastic material constituting the blanket (3) is poured inside the cavity in fluid state, until filling the inner volume of said cavity (19), including the mould key seat (20) and the insert (5) introduced. Both the grooves (12) and the striations (13) defined in the insert (5) increase their surface and therefore increase the adherence of said insert (5) with the material of the band (3) surrounding it.
Additionally, the separating ribs (11) defined in the top face (8) of the insert (5) prevent the direct contact of this insert (5) with the sheet of stiffening material (15), avoiding contaminations and guaranteeing good adherence as it allows the entry of a layer of plastic material between the sheet of stiffening material (15) and the insert (5), as detailed in
Then the blanket is extracted from the mould (16), producing a blanket with cylindrical cortex geometry, with the key (4) provided with an insert (5) embedded inside and the handling area of the insert is cut.
In
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/ES2016/070440 | 6/10/2016 | WO | 00 |
