EP1693114A2

EP1693114A2 - Control device for spraying products used in the treatment of leather

Info

Publication number: EP1693114A2
Application number: EP06110162A
Authority: EP
Inventors: Giuseppe Rossetto
Original assignee: PGM Automation Srl
Current assignee: PGM Automation Srl
Priority date: 2005-02-21
Filing date: 2006-02-20
Publication date: 2006-08-23
Also published as: EP1693114A3; ITVR20050026A1

Abstract

A control device, which can be applied to product dispensing means used in machines for processing leather and application on release paper and in particular for continuous product spraying, consists of a volume variator (10) connected to a conduit (22) in which the delivery and pressure are controlled along the duct (23) between the pump (25) and the nozzle (24) to which the conduit is connected. The volume variator (10) makes it possible to accumulate product, inside the dosing unit (20), close to the reversal direction stages of the nozzle (24) and to gradually dispense the accumulated product when the nozzle moves over the central part of the surface to be processed.

Description

TECHNICAL FIELD

This invention concerns a control device which can be applied to product dispensing means used in machines for finishing leather and in systems for crust coating.
In particular the application can be used in the sector of devices which allow products to be sprayed directly on leather or on release paper.
More specifically, this invention refers to a device that varies the amount of dispensed product according to the position of the spray gun.
This resolves the problems relative to the nonuniformity of the pigmentation and the thickness of the dispensed product in the areas where the spray movement is reversed (edges).
This invention can be applied in the production sector of machines for leather processing and in particular in the sector of machines for spraying products used in leather pigmentation and crust coating.

BACKGROUND ART

It is known that in many cases leather processing requires the so-called finishing stage in which colouring or chemical or other types of products or preparations are spread on the surface to be processed.
In the leather finishing sector, an important objective for the operator is to satisfy, as far as possible, the specifications expected by the end user, paying increasingly more attention to the durability of the articles, their appearance, their easy maintenance and to the fact that they must stand up to the most severe conditions when in use.
This requirement involves a constant search for new products, new methods of application and new proposals of types of leather.
The finishing of the leather must make it possible to obtain an article that is as natural as possible so as to make the biological nature of the material evident and unmistakable.
It must also conceal any defects in the leather which, even if one attempts to have them accepted as natural features of the products, nevertheless tend to lead to rejecting a purchase in favour of an article with fewer defects or none at all.
It is necessary to ensure the possibility of easy maintenance and care with the appropriate products available on the market, and light fastness must be as high as possible particularly in the case of seat coverings for cars/aeroplanes and clothing.
The leather finishing process must guarantee resistance to abrasion, long-life, compatibility with dry cleaning technology and resistance to rubbing when dry or wet.
Adhesion of the finish must be perfect, and the quality and mechanical requirements expected and currently respected by finishing technicians are numerous and severe.
The task which immediately follows finishing is to maintain the production standard of the articles and the uniformity of the supply for a product like leather which, being a biological material with different origins, has variable features.
The product is usually applied by means of direct spraying on the leather or on release paper for crust coating.
Application is generally carried out by means of spraying machines which foresee the use of a spray gun positioned on a carriage that moves along a beam positioned transversally to the direction of movement of the surface being processed.
During the stages in which the product is sprayed, the spraying device consisting of the spray gun moves to the right and the left, with respect to the leather infeed direction, by means of the carriage on which it is mounted, so as to move from one edge to the other of the leather or the release paper, until the entire surface to be processed has been covered.
This working procedure has, however, demonstrated some drawbacks, mainly regarding the difficulty in keeping the amount of dispensed product uniform.
In fact, in some cases the surface processed with this system presents overlap areas with excess product at the edges, alternating with other central areas in which the product is thinner.
This is due to the swinging movement of the spray gun and the simultaneous infeed movement of the leather or the release paper.
To overcome this drawback, measures have been adopted in order to make the spreading of the product on the leather more even.
The first attempt was to programme the movement of the spray gun so that it continued spraying beyond the outer edge of the leather. While improving the quality of the spraying process, this nevertheless caused considerable product waste with costs that proved excessive and totally uncompetitive.
Another attempt, which however led to even more uncertain results, was to intermittently move the two coupling points on which the carriage holding the spray gun slides.
This method does not in fact prevent the formation of overlap areas, but at most makes the spreading areas more parallel, without resolving the problems of double-layer coverage typical of the edge areas.

DESCRIPTION OF THE INVENTION

This invention proposes to provide a device that can eliminate or at least reduce the drawbacks described above.
The invention also proposes to provide a device that makes the spreading of the leather preparation as uniform as possible, not by intervening on the movement of the nozzle but on the amount of dispensed product which is appropriately controlled by the device according to the invention.
This is achieved by means of a control device for spraying the product on the surface of leather or the like, the features of which are described in the main claim.
The dependent claims describe advantageous embodiments of the invention.
The main advantages of this solution, in addition to all those deriving from the construction simplicity, concern first of all the fact that a more or less uniform spread of the product on the surface being processed is achieved.
The device according to the invention also presents the by no means indifferent advantage of solving the problems described above relative to the difficult uniformity of the spread of product without negatively affecting plant costs, thus improving not only the quality of the process but also being more advantageous from the production point of view.
The device according to the invention is applied on the duct system of the product which is dispensed to the spraying nozzle and consists of a unit which can control the delivery and therefore the pressure of dispensed product according to the position of the nozzle.
In other words, the control device is constructed in such a way that when the nozzle is close to the centre of the leather the amounts of dispensed product are normal, while close to the edges the amounts of product are gradually reduced until they are minimal at the point of carriage reversal, when it begins to move back towards the other edge.
The dosing device is equipped with a linear motor, which causes the movement of piston acting on a dosing unit to which the nozzle delivery tube is coupled.
Delivery control is also possible for products made up of several components, mixed together immediately before being dispensed by the nozzle. In this case, a number of control devices are used equal to the number of the components. These devices will be synchronised, adjusting the delivery of the dispensed product on the basis of the ratio of each individual component.
The device that allows the use of this technology is positioned in parallel with the nozzle feed circuit, so that product can be accumulated when the nozzle is close to the edges and then dispensed in progressively varying and controlled amounts close to the central area.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become evident on reading the following description of one embodiment of the invention, given as a non-binding example, with the help of the accompanying drawings, in which:

figure 1 represents a schematic view of the overall dosing unit according to the invention;
figure 2 represents a prospective schematic view of the dosing unit according to the invention;
figure 3 shows a schematic plan view of the dosing unit;
figure 4 shows a schematic partial cross-section view of the dosing unit according to the line A-A in figure 3.

DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

With reference to the attached figures, the dosing device according to the invention, indicated overall with 10, is equipped with a linear motor 11 which surrounds a fixed magnetic shaft 12 forming the fixed part of the motor.
The shaft 12 is fixed between two parapets 13 and 14 and the movement of the linear motor 11 is kept in trim by ball screw type guides 15, integral with the fixed bed 16.
Above the linear motor 11 is a plate 17 which, in turn, moves a simple effect piston consisting of a rod 18 with a head 19, representing an actual piston, which acts inside the cylindrical chamber of a dosing unit 20.
The opposite end of the dosing unit with respect to the end where the rod 18 is inserted is fitted with a coupling 21 which is connected to a conduit 22 that intercepts the delivery duct 23 of the product to be dispensed on the leather by means of the spraying device 24.
The conduit 22 is in fact connected to the delivery duct 23 in an intermediate position between the spraying nozzle 24 and the pump 25.
The variation in delivery and pressure in the conduit 22 controlled by the dosing unit 20 and more specifically by the movement of the rod 18 and the relative piston 19 inside the unit 20 by means of the linear motor 11, leads to a variation in volume in the conduit 22, with a consequent variation in pressure in the duct 23 of the nozzle 24.
It is therefore evident that the control unit 10 described here can control the delivery and the pressure of dispensed product according to the position of the nozzle.
In other words, the device moved by the linear motor and controlled by appropriate electronics will begin to accumulate product, inside the dosing unit, when close to the direction reversal stages of the nozzle 24 and to gradually dispense the accumulated product when the nozzle moves over the central part of the surface being processed.
The result achieved is a normal amount of product dispensed in the central area and a progressively reduced amount dispensed in the outer areas, becoming minimal near the edges.
According to another embodiment, the linear motor 11 can be replaced by a brushless rotary motor with a shaft fitted with a toothed pulley that can engage with a rack integral with the rod of the simple effect piston 18.
The invention is described above with reference to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations that lie within the sphere of technical equivalents.

Claims

A control device which can be applied to product dispensing means used in machines for processing leather and application on release paper and in particular for continuous product spraying, characterised in that it consists of a volume variator (10) connected to a conduit (22) in which the delivery and pressure are controlled along the duct (23) between the pump (25) and the nozzle (24) to which the conduit is connected, and in that the volume variator (10) makes it possible to accumulate product, inside the dosing unit (20), close to the reversal direction stages of the nozzle (24) and to gradually dispense the accumulated product when the nozzle moves over the central part of the surface to be processed.
A control device according to the foregoing claim, characterised in that the volume variator (10) consists of a simple effect piston (18) with a head (19), representing an actual piston, that acts inside the cylindrical chamber or a dosing unit (20).
A control device according to either of the foregoing claims, characterised in that the head (19) of the dosing unit (20) is positioned at the end of a rod (18) in turn activated by a linear motor (11).
A control device according to any of the foregoing claims, characterised in that the linear motor (11) is positioned over a fixed magnetic shaft (12) on which it slides, the shaft being fixed between two parapets (13, 14) and the movement of the linear motor (11) is kept in trim by ball screw type guides (15) integral with the fixed bed (16).
A control device according to any of the foregoing claims, characterised in that according to another embodiment the linear motor (11) is replaced by a rotary motor with a shaft equipped with a toothed pulley that engages with a rack integral with the mobile rod of the simple effect piston (18).