REVERSIBLE COATING MACHINE FOR ROLLER FINISHING OF SKINS AND THE LIKE

DESCRIPTION

Field of the Invention

The present invention relates to the field of finishing processes for coating leather and similar sheet materials. More precisely, it concerns a special coating machine for the roller finishing of skins, configured to operate reversibly, i.e. with so-called “synchro” and so-called “reverse” operation.

Background of the Invention

Conventional roller coating machines are well known in this field for coating leather with liquid finishing chemicals that give the leather the desired final surface properties. They are configured to operate only in synchro mode, i.e. with the engraved roller rotating in the feed direction of the underlying leather feeding system, or to operate only in reverse mode, i.e. with the engraved roller rotating in the opposite direction to the above- mentioned feed direction.

In both types of machine, there are doctor blades that act as scraper blades for the coating material, which are arranged resting on the roller in different positions depending on whether the machine is synchro or reverse (in the first case on the inlet side of the material, in the second case on the opposite side). When natural skins, i.e. loose pieces and not material wrapped in rolls, are processed, the synchro machine also requires a detachment system on the opposite side to the inlet side, i.e. the outlet side, to counteract the natural tendency of the skins to stick to the honeycombed surface of the engraved roller. Such a system can be automatic in nature, and various solutions have been proposed in this regard (e.g. counter-rotating closed-loop sleeves, toothed rollers of various shapes and sizes), but often, still speaking of synchro-only machines, manual intervention is also simply used.

More recently, however, reversible machines, i.e. machines capable of working in both reverse and synchro modes, have been developed. These machines therefore have two doctor blades in opposed positions, which perform their function depending on whether the machine operates one way or the other. In these machines, however, the presence of the reverse mode doctor blade in the leather outlet area creates a complication with regard to the skin removal function in the synchro operating mode. In fact, the basic configuration of these machines, invariably designed in its original configuration to be efficient, in the reverse mode, on a very wide range of items, has limitations in the possibility and/or space for the positioning of the support and control system of the toothed roller series adopted for the skin detachment function. The detachment system is located close to the position typically occupied by the reverse mode doctor blade, and since the simultaneous presence of the detachment system is not compatible with the operation of the machine when working in the reverse mode, it follows that the entire detachment system must be removable and repositionable.

On the other hand, when the machine is working in synchronous mode the reverse doctor blade is not in use, and to prevent it from creating unnecessary or problematic bulk, it is removed, so that when switching from synchronous to reverse mode, it is necessary to stop the machine, remove the leather detachment device, and then position the reverse doctor blade. The latter operation, besides being time-consuming, is made very difficult by the fact that the machine that also operates in reverse is fitted with a conveyor belt, which makes access to the machine space, where the replacement is to be carried out, more difficult.

In general, it can therefore be said that when the need arises to change an article and/or process that requires switching from reverse to synchro or vice versa, the amount of operations and adjustments to be carried out inevitably entails a loss of time that can be estimated as 30-45 minutes. The fundamental complicating factor for this type of machine is ultimately linked to the need for a motorized accessory device for detaching the skins, which considerably increases the complexity of the machine, also in view of the need to comply with all the increasingly stringent requirements introduced by the most recent safety regulations.

Returning specifically to the doctor blade, it is, as is well known, a particular blade that in the operating position is placed in contact with the engraved roller, typically made of chrome-plated steel, thus creating a sort of basin that contains the chemical for coating. The latter exits from the slot that is formed at the point of proximity between the doctor blade and the engraved roller. The amount of product that is dispensed is strictly dependent on the size of this slot, which is in turn determined by the pressure with which the doctor blade insists on the surface of the engraved roller. When the system is perfectly adjusted, the amount of product passing through coincides exactly with the amount of product able to fill the engravings of the engraved roller, which are created precisely for the purpose of fixing the amount of product that must reach the leather to be treated.

Too high a roller pressure will prevent the roller from sliding properly, while a pressure below optimum will result in the formation of a passing film of liquid product, in addition to the desired product already present in the engravings, which will spread on the leather, generating defects. Present commercial machines employ doctor blades driven by air pistons that control their opening/closing status relative to the contact position with the roller, after which the operator can adjust the pressure that the doctor blade must exert on the engraved roller by means of manually operated thumbwheels associated with worm screws. This pressure differs from process to process, depending in particular on the viscosity of the chemical product to be applied and the linear speed of the conveyor belt and rotation of the engraved roller.

Since the precise control of the pressure of the doctor blade on the engraved roller is a decisive aspect for controlling the amount of treatment liquid to be dispensed and thus for the success of the process, motorized doctor blades have been proposed by the same applicant, with digital control to allow the operator, in a very strict manner, to choose and apply the desired pressure on the engraved roller, also making the same operation reproducible over time. This has made it possible to optimize the way the doctor blade is used in its pressing function to define the quantity of chemical product to be dispensed, through the engraved roller, onto the leather.

Summary of the Invention

Considering the state of the art described above, the applicant has now come up with a surprisingly effective solution, providing a synchro-reverse coating machine, and its method of operation, which through a configuration refinement allows it to overcome the problems of the already known machines, in particular those mentioned above of bulk, structural complexity, and the need for long downtimes that limit productivity, resulting from the presence of the additional detachment device for operation in synchro mode.

The synchro-reversible coating machine for roller finishing of skins and the like which, according to the present invention, achieves the aforementioned result, has the essential features listed in the first of the appended claims. An operating method practised, still according to the invention, in the context of such a machine, essentially has the characteristics of the appended claim 8. Other additional features are the subject matter of the dependent claims.

Brief description of the drawings

The features and advantages of the synchro-reverse coating machine for roller finishing of skins and the like, and the method thereof, according to the present invention will be more clearly seen from the following description of one of its embodiments, provided by way of example and not limitation, with reference to the accompanying drawings in which:

- figure 1 and figure 2 show schematic side views of the machine according to the invention in two successive operating steps in synchro mode.

Detailed description of the invention

With reference to the aforesaid figures, the invention is essentially based on the intuition that by suitably configuring a reversible type roller coater, with a reverse mode doctor blade equipped with independent motorization, such a machine can effectively work also in synchro mode without requiring the installation of auxiliary detachment rollers (or equivalent devices), nor requiring any disassembly operation when switching from one operating mode to the other. To this end, the sole and simple movement of the reverse doctor blade, achieved by appropriately configuring the control system of the machine, as it approaches the roller to a position of interference with the skins being processed on the roller, has surprisingly proved to be capable of promoting their detachment and ensuring their deposit on the underlying outlet conveyor system.

Going into further detail, the figures show a schematic side view of the main functional elements of the machine; obviously a more analytical description of these elements is not necessary, insofar as the details of their design are in themselves well known to a person skilled in the art.

The machine thus comprises at least one cylindrical engraved roller 1 , which rotates about its central axis X, and a feeder 2, e.g. with conveyor mats, of the skins towards roller 1 in a plane A essentially tangential to the roller, according to a linear feed direction Y and a feed direction evidently oriented towards the roller. The feeder 2 is located on the inlet side of the roller itself. A contrast roller 3 is traditionally placed below the engraved roller 1 , defining therewith the inlet area of the skins brought in by the feeder.

Also arranged on the inlet side is a first doctor blade 4 for spreading liquid onto the skins, cooperating as known in contact with the side surface of the roller along a generatrix thereof. This first doctor blade 4 is the doctor blade intended for material distribution functionality in the synchro operating mode, i.e. when the roller rotates about the X-axis in a direction that is, at the inlet point of the skins, concordant with the feed direction Y.

A second doctor blade 5 for the distribution of spreading material is arranged on the outlet side of the roller, diametrically opposite the inlet side, and on which a traditional system 6 for conveying the coated skins, exiting from roller 1 , extends. The second doctor blade 5 is in turn designed to cooperate with the side surface of roller 1 along a generatrix thereof. This second doctor blade is the so-called reverse mode doctor blade, meaning that it is the one designed to work in distribution when the roller rotates in the opposite direction to the feed direction of the incoming skins. Both doctor blades have known structures that are neither described nor illustrated in detail. The second doctor blade 5, or reverse mode doctor blade, however, is notably equipped with its own independent motorized means, which allow for position control at least when approaching and moving away from the roller.

In addition to these motorized means of the second doctor blade 5, or reverse doctor blade, the drive means of the machine evidently include a motorization to drive the roller 1 , not shown, in rotation, all of which is subservient to control means (electronic control units as per the technology commonly used in the sector) configured to control the machine both in synchro operating mode, in which the first doctor blade 4 is activated for the function of spreading material, and in reverse operating mode, in which the second doctor blade 5 is activated in its traditional function of spreading material.

If the reverse operation takes place in the traditional manner, the specificity of the machine according to the invention is linked to the synchro operating mode, which is precisely that of which representations are provided in the figures. In fact, in spite of the lack of auxiliary means/devices for the detachment of skins, such as traditional rollers, a lacking which is a characteristic of this machine and which can also extend to any assembly arrangements, the detachment of the skins at the outlet is ensured by the fact that the control means, activating the reverse doctor blade 5 through its independent motorization, bring the latter, precisely the relative blade, closer to the engraved roller 1 until a position of interference with the skins exiting the roller itself to counter adhesion phenomena and cause the skins to fall onto the outgoing conveying system 6. Thus, it is the movement of the reverse motorized doctor blade 5 that is used in a surprisingly effective manner, not only to adjust the position of the blade in its traditional distribution function, but also in synchro mode. In the latter, instead of an unnecessary encumbrance or even a component to be removed, the doctor blade takes on the fundamental role of a detachment device, avoiding the need for auxiliary component assembly and thus leaving the machine configuration unchanged, with all the advantages that this entails.

Figure 1 thus shows a piece of leather T being treated by the engraved roller 1 , with the synchro blade 4 being operational for its function of distributing the material to be coated onto the roller, and the leather about to arrive with its leading edge at the reverse doctor blade area 5 on the outlet side. There, interference with the blade of the doctor blade (figure 2) causes a flap of the head to detach, followed by the rest of the body of the piece/skin, until it falls onto the conveyor system 6.

In practice, the control system provides for different settings, or setting programmes, of the position, and thus the pressure of the reverse blade/doctor blade, each of which can be selected or preferably assumed automatically depending on the specific synchro or reverse operating mode, and thus on the different function/purpose (liquid distribution in reverse mode, skin detachment in synchro mode).

The setting for the skin detachment function can be such that in the interference position the end edge of the blade/doctor blade is at a distance of 0.1 to 0.5 mm from the side surface of the roller. In the context of this setting, or depending on it, the doctor blade stroke between this interference position and a rest position is comprised between 50 and 80 mm. Optionally, the machine control system can comprise sensor means for detecting the position of the skins on the engraved roller 1 , configured to activate the second doctor blade or reverse doctor blade 5 according to a position signal obtained from the position sensors, with an appropriate timing to best perform the detachment function without otherwise disturbing the coating operation.

According to the invention, an expedient is thus provided that proves to be surprisingly effective, managing to optimize the components already present, without introducing new ones, and allowing the machine to practically perform all the machining operations (synch ro/reverse) becoming universal very quickly and in total safety for the operators. 5. As mentioned above, the machine can always work without needle rollers or equivalent auxiliary devices solely intended for detaching the skins exiting the engraved roller, but its infrastructure can also generally be free from attachment means for the assembly of such needle rollers or equivalent auxiliary devices.

The present invention has been described hereto with reference to preferred embodiments thereof. It is intended that other embodiments may exist which relate to the same inventive core, all falling within the scope of protection of the claims indicated below.