Patent Application
20050211124
This invention concerns a flexographic printer with temperature-regulated sections and vapour extraction, and more specifically, a flexographic printer including a casing fitted with interior means of division that form suitably insulated sections containing various printer components, with a fluid at a regulated temperature circulating through these sections.
A flexographic printing machine typically consists of support structures on which one or more back-pressure cylinders are mounted, which support a moving continuous band of material to be printed, and one or more flexographic printing heads, each of which consists of a cliché-holder cylinder that can make contact with the cited band to be printed and an ink-well or inking unit, which includes at least one ink cylinder to supply ink to the cliché-holder cylinder. Each print head can be associated with its respective back-pressure cylinder having a relatively small diameter or all the print heads can be located around a single, central, large diameter back-pressure cylinder. The incorporation of several print heads is employed to successively print the continuous band in different colours. In this way, the first print head deposits ink of one colour on the band to be printed and the successive heads superimpose inks of other colours. To prevent colour mixing it is necessary to dry the previous colour ink before applying another. Drying the ink involves the evaporation of the pigment diluent it contains and this is usually accomplished using drying boxes located between the print heads, which include the means of blowing hot air onto the printed band, together with the option of air suction to extract the air contaminated with the solvent vapour from the area of influence of the drying box.
It is also usual to protect this type of printing machine with casing or fairings that basically meet certain safety functions, preventing operator access to dangerous components and health functions by reducing the level of noise reaching the operators and also improving the machine's visual aspect. In order to comply with the cited soundproofing function, the fairings tend towards greater levels of insulation and sealing, with the acoustic insulation also doubling as heat insulation.
Unfortunately, this combination of insulation and sealing also involves the following two disadvantages:
The heating problem generally affects all the printer components and mechanisms, but very specifically the large-diameter central back-pressure cylinder and its support structures, in those machines fitted with them. This central back-pressure cylinder must be manufactured with certain dimensional tolerances, especially cylindricity, which are very close and must be maintained throughout operation periods. Because the drying boxes produce the hot air impulsion directly over localised areas of the back-pressure cylinder, cylinder expansion, especially when operating slowly, can produce deformation that exceed the permitted tolerance. The expansion deformation suffered by the support structures also negatively affects the machine's operation.
There are various well-known devices for cooling or maintaining the back-pressure cylinder at a constant temperature by means of circulating water. One such device consists of fitting the cylinder with a double steel wall that provides an intermediate space through which the cooling water is able to circulate.
Patent U.S. Pat. No. 5,048,418 describes a flexographic printing machine with support structures or beds fitted with the means to regulate the temperature. These means consist of one or more closed channels for the circulation of a cooling or temperature-regulating fluid. The channels follow spiral paths to cover at least the support structure zones where the back-pressure cylinder is mounted.
However, both the cited means for cooling the cylinder and the means of cooling the support structure or bed are designed for very specific areas of the machine, but do not provide any overall temperature regulation inside the casing.
With respect to the problem of solvent vapour concentration, the previously described means of extraction associated with the drying boxes are known, but they are not sufficient to prevent an accumulation of solvent vapour of the lower section inside the insulated casing. The vapour produced by commonly used solvents is highly inflammable and accumulations inside the casing normally exceed a determined lower explosion limit, which means that a high-level of intrinsic protection must be employed in the printer's electrical devices and components, the measurements of which are strictly regulated by industrial codes in most countries. The implementation of the cited means of high-level protection and safety involves high economic costs of the components and, in addition, does not reduce the concentration of the explosive vapours inside the casing.
The objective of this invention is to produce a flexographic printer with a surrounding casing and interior dividing means in order to produce at least two sections, fitted with the means to regulate the temperature and the vapour concentration levels inside the casing that are capable of providing a suitable operating temperature for the component parts and, at least in one of the described section, the one housing all the drive means and electrical or electronic devices, maintain a vapour concentration level below a preset lower explosion limit, which will make the application of the high-level means of protection unnecessary for the described electrical devices.
Another objective of this invention is to provide a flexographic printer with the additional advantage of protecting those elements associated the drives from dirt and to permit access for ease of cleaning in those areas exposed to possible impregnation by ink.
The previous objective is achieved in accordance with this invention, by producing a flexographic printer of the type consisting of a frame on which are mounted at least one rotating back-pressure cylinder and at least one print head, which consists of a cliche-holder cylinder that can make contact with a band to be printed supported on the cited back-pressure cylinder and an inking unit, consisting of at least one inking cylinder that supplies ink to the cited cliché-holder from a tank. The rotation of the various is provided by suitable drive means, generally electric motors. The components of the flexographic print head can be moved closer to or farther away from the cited back-pressure cylinder, so that the machine is also fitted with the means of driving this movement the said components, which is also usually provided by electric motors. The printer of this invention is also the type that includes the means for drying or curing the film of ink deposited on the band to be printed and a surrounding casing. The flexographic printer of this invention is characterised in that the cited surrounding casing, in combination with interior dividing means, delimits at least two sections, through which at least one fluid circulates that is introduced at a temperature regulated by a means of impulsion and is sucked out by means of extraction, with the cited sections being sufficiently closed to provide a specific atmosphere inside at an efficient controlled temperature.
In addition, in one of the said sections, those printer organs that produce a continuous degree of solvent vapour generation are concentrated, such as the inking cylinders, ink tanks and other inker components etc, while those printer devices that contain electrical and/or electronic elements, such as drive motors, power supplies and control etc, are concentrated in the other section, of which there is at least one. Both sections are sufficiently insulated from each other so that the degree of solvent vapour leakage from the first to the second is secondary, with the circulating volume of the said fluid being sufficient for the interior atmosphere of at least the second section that houses the electrical and/or electronic components has a vapour concentration from the ink that is below a lower preset explosion limit. This lower explosion limit is established in accordance with strict regulations in most countries or, in the absence of this, it may be calculated.
The fluid circulating through the cited sections should be a gas; more specifically it should be air.
According to a preferred exemplary embodiment of the invention, the cited back-pressure cylinders, cliche-holder and inker are arranged between the first and second support structures which make up the cited frame, while the cited means of rotation drive and movement are arranged on the outer sides of both the first and second support structures. The cited means of division are arranged in relation to the first and second support structures in order to create three of the said separated sections in co-operation with the surrounding casing: a first section between the first and second support structures, where the cylinders and cited means of drying are housed; and the second and third sections in exterior zones of the first and second support structures, where the means of rotation drive and movement are housed. However, the invention also contemplates the possibility of arranging the means of division in relation to only one of the support structures so that only two sections are formed: a first section between the first and second support structures, where the cylinders and means of drying are housed; and a second section in an exterior zone of the first support structure, where the means of rotation drive and movement are housed. The essential part, in both cases, is that the first section houses the all the elements that are in direct contact with the ink and, therefore, where continuous evaporation of the solvent takes place, is sufficiently isolated from the second and/or third section where all the means of drive are concentrated (in general, the electric motors) and electrical and/or electronic components associated with the said means of drive, such as connectors, switches, relays and fuses etc. Thus, in the first section, the risk of explosion is practically eliminated thanks to the mentioned air circulation, which guarantees that the said solvent vapour concentration is maintained below the preset lower explosion limit, which will also avoid the need to install costly, high-level protection devices for the electrical elements whish would otherwise be necessary.
In addition to the actual motors and as is usual in this type of machine, the means of drive include also includes the means of guidance and mechanical transmission, which here, are arranged in the said second and third sections, and therefore safeguarded from possible ink impregnations, with the said first section, together with the components it contains, being easily accessible for cleaning.
The mentioned means of air flow impulsion consists of at least one fan connected to a conduit for the entry of the fluid, which is fitted with branches with various impulsion mouths distributed inside the said first, second and third sections. The mentioned means of extraction consists of at least one fan connected to a fluid exit conduit fitted with branches with various suction connections that are similarly distributed inside the first, second and third sections. Because it is normal to employ a solvent for the ink, the vapour of which is denser than air, at least one of the said suction connections is located in the lower zones of the first section, which contains the cylinders and means of drying, in order to extract the solvent vapour coming from the ink drying and evaporation, together with the exiting fluid or air.
Just as was described earlier, the flexographic print head or heads can be moved closer to or farther away from the back-pressure cylinder, of which there is at least one. Thus, the cited components are mounted in a movable fashion on suitable guides fixed on the support structures. Since the cliché-holder cylinders are arranged in the first section between the support structures and their respective means of rotation drive and movement are located in the second and third sections arranged on the other sides of the support structures, these support structures contain apertures by which part of the means of drive for the flexographic print head components are moved.
According to a construction example of this invention, the means of division consist of curtains of fluid, in other words, air, driven from impulsion mouths connected to branches of the cited air entry conduit and located in relation to the said first and second support structures in the upper section inside the casing. These curtains are sucked from several of the said suction connections, which are connected to branches of the exit conduit and located in a lower zone of the casing. According to another construction example, the support structures from closed panels in which the only apertures are those previously described above, by which the flexographic print head components are moved, and the means of division consist of elastic and/or flexible and/or sliding elements that cover the cited apertures. It must be pointed out here that both construction examples are fully compatible and can exist in the same printer design. It is not necessary for the casing and the means of division to provide a complete seal for the sections, but that they are sufficiently closed in order to guarantee their intended purposes.
Conventional drying boxes may be employed for the means of drying or cutting, which are connected here by one side to specific means of impulsion, which blow previously heated air over the printed band and by the other side to a branch of the cited exit conduit connected to the said means of general casing suction in order to suck the air and solvent vapour from the ink.
The air from the drying box is heated by some means of heating, such as a fuel burner or electric element. The air that enters the sections at a regulated temperature via the entry conduit is heated/cooled by means of, for example, a water/air heat exchanger located outside the sections.
As an advantage, the operation of the said heat exchanger unit and/or blower fan and/or extraction fan for regulating the entry flow rate and fluid flow rate and exit solvent vapour are controlled by certain electronic means of control in function of a signal received from at least one temperature sensor located inside the surrounding casing. The temperature regulation control is further completed by means of the said temperature sensors installed at various points in the said first, second and third sections, together with various means of register driven by their respective means of drive in various branches of the said entry and/or exit conduits. In this case, the cited electronic means also control the operation of the cited means of drive for the means of register in order to regulate the flow rate and temperature of the entry fluid and fluid flow rate and exit solvent vapour in different zones of the various sections in function of the signals received from the said various temperature sensors.
The printer configuration of this invention can consist of either several flexographic heads associated with a single common back-pressure cylinder, or several flexographic heads, each associated with its own back-pressure cylinder. When there is only one common back-pressure cylinder, this may be optionally fitted with any of the known temperature regulation devices, such as the water cooling device described above.
The characteristics and advantages of this invention are made more evident by the following detailed description of a preferred construction example with reference to the attached drawings, in which:
First referring to
The essential characteristic this invention is that the cited surrounding casing 6, in combination with interior dividing means 11, delimits at least two sections and, in general, three sections, designated here as the first, second and third sections 12a, 12b and 12c through which at least one fluid circulates that is introduced at a temperature regulated by a means of impulsion 21 and is sucked out by means of extraction 8 by suction (
Preferably, the cited fluid is a gas and more preferably is air, although other gases, such as nitrogen, may also be employed.
As an advantage, the cited back-pressure cylinders, cliché-holder and inker 2, 4 and 5 and the said means of drying are installed between certain respective internal facing faces of the cited first and second support structures 1a and 1b of the said frame 1, while the cited means of rotation drive 9 and 10 are arranged on respective external faces, opposite the cited facing faces of both the first and second support structures 1a and 1b.
Just as will be explained below, with reference to
The purpose of the separated sections 12a, 12b and 12c is to isolate zone 12a in which the cylinders are located and consequently where the ink is handled, of zones 12b and 12c where the cylinder drive means are located, including the electric motors, and the electrical and/or electronic components and devices associated with the said drive means. In addition, this separation also provide increased guarantees that in the said zone, which houses the electrical and/or electronic components and devices, in other words, the second and/or third sections 12b and 12c, the cited solvent vapour concentration is below the said preset lower explosion limit. This is achieved by means of the cited air circulation at the regulated temperature, which also guarantees a suitable operational temperature in all sections 12a, 12b and 12c.
As an additional advantage, it must be mentioned that the drive means 9 and 10 include, in addition to the motors and power supply and control devices, the means for guidance and mechanical transmission which, in the printer of this invention, are also installed in the said second and third sections 12b and 12c. In this way, all the elements and mechanisms associated with the drive means 9 and 10 are safeguarded from possible impregnation by ink, with the first section 12a and the elements it contains being easily accessible for cleaning.
If we briefly examine
Just as shown in
According to the preferred construction example shown in
Now, in relation to
The mentioned means of drying or curing consist of conventional drying boxes 19, which are connected by one side to the means of air impulsion directed towards the printed band and by the other side to at least one branch of the cited exit conduit 14 connected to the said means of suction 8 to suck the said fluid and solvent vapour produced by the ink. The air blown by the said means of impulsion, which consist of an impulsion fan coupled to a conduit connected to the entrance to the drying box 19, is previously heated, for example, by means of a fuel heater or an electric heating element.
It should be noted that the cited means of air impulsion and heating for the drying boxes 19 are independent of the means of introducing 21 the air at regulated temperature which circulates through the sections. On the other hand, the means of circulation 8 are common. This is because the circulating air entry may require heating, but it might also require cooling in function of the general operating conditions. Therefore, the introduced air at the regulated temperature is heated/cooled by means of suitable means, such as a water-air heat exchanger 20 located outside the sections.
As an advantage, at least one temperature sensor is installed inside the surrounding casing 6, together with the electronic means to control the operation of the said heat exchanger 20, the blower fan 21 and the extraction fan 8 in order to regulate the flow rate and temperature of the entry fluid and the flow rate of the exit fluid and solvent vapour in function of a signal received from the said temperature sensor. According to a more complete variant, the printer of this invention includes several of the said temperature sensors installed at various points of the said first, second and third sections 12a, 12b and 12c, together with the means of inspection in various branches of the said entry 13 and exit 14 conduits, the means of inspection of which are driven by their respective drive means. Here, the said electronic means control the heat exchanger operation 20, the blower fan 21, extraction fan 8 and the cited drive means of the means of inspection in order to regulate the flow rate and the temperature of the entry fluid, together with the exit flow rate of the fluid and solvent vapour at the various zones of the first, second and third sections 12a, 12b and 12c, in function of the signals received from the said temperature sensors.
Although the invention has been described in relation to specific construction examples, these examples have a merely illustrative character and do not limit the scope of this invention, which is defined in the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/ES02/00135 | 3/20/2002 | WO | 5/2/2005 |
