Technical field

The present invention relates to an apparatus for injecting chemical components into a flow of loose wooden material.

Background Art

It is known that the process of fabricating panels from particles of wooden material (chipboard, MDF, OSB etc.) involves a step of mixing preset quantities of loose wooden material with suitable doses of chemical components, i.e. adhesives and additives in general, which precedes the step of forming the mattress and the subsequent pressing thereof so as to obtain a panel.

This mixing step evens out the distribution of the chemical components in the mass of loose wooden material within special mixers so as to obtain a smooth paste.

The injection of the chemical components can occur directly within the mixer or, more preferably, upstream of the inlet into the mixer to obtain a pre-mixing of the particles of wooden material and of the chemical components.

A method and a system that implement this pre-mixing are described in EP 1 468 799 Al , in the name of the same Applicant. The system, in particular, comprises a device for feeding loose wooden material, which is associated with the inlet of a mixer via the interposition of a hopper which is provided internally with nozzles for injecting adhesive directly into the flow of wooden material that passes through it.

This type of system, while enabling an optimal mixing of the wooden material and of the adhesive, is not without drawbacks, among which is the fact that it must necessarily be fitted out to send an airflow along the hopper, i.e. to generate a partial vacuum at the inlet of the mixer, so as to direct the jet of adhesive towards the flow of loose wooden material and limit the smearing of the inner wall of the hopper.

In any case the hopper, over time, tends to get dirty, necessitating interventions for cleaning and replacement, with consequent shutdown of the system and increase in running costs.

Also, solid deposits of non-negligible size form on the inner wall of the hopper over time. If such deposits should accidentally detach, falling into the mixer, it cannot be guaranteed that they will be crushed and homogenised in the paste being processed, with consequent formation of discards.

These aspects limit the possibility of use and the flexibility of application of this type of system.

Disclosure of the Invention

The aim of the present invention is to eliminate the above-mentioned drawbacks of the known art, by providing an apparatus for injecting chemical components into a flow of loose wooden material, which solves the problem of smearing of the region in which the injection of the chemical components is performed, and in particular the injection of the adhesive, generally of the thermosetting type, without necessitating auxiliary apparatuses for the delivery of air under pressure upstream of the injection region and the aspiration of air downstream of that region.

Within this aim, an object of the present invention is to prevent the formation of lumps in the paste of loose wooden material and chemical components being processed.

A further object of the present invention is to be easily applied even on mixing systems that are already installed.

A further object of the present invention is to provide a simple structure, that is easy and practical to implement, safe to use and effective in operation, and has relatively low costs.

This aim and these objects are all achieved by the present apparatus for injecting chemical components into a flow of loose wooden material, comprising a tubular body which is provided with at least one inlet, which can be associated with means for feeding loose wooden material, and with at least one outlet, which can be associated with a mixer, and which is crossed internally by a flow of said loose wooden material from the inlet toward the outlet, and means for injecting at least one chemical component toward the flow of loose wooden material, which are associated internally with respect to said tubular body, characterized in that it comprises scraper means which are associated with the internal wall of said tubular body and can move tangentially with respect to it, means being further provided for actuation with a relative motion of at least one of the tubular body and the scraper means with respect to each other.

Brief description of the drawings

Further characteristics and advantages of the present invention will become better apparent from the description of a preferred, but not exclusive, embodiment of an apparatus for injecting chemical components into a flow of loose wooden material, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic plan view from above of an apparatus for injecting chemical components into a flow of loose wooden material, according to the invention;

Figure 2 is a schematic cross-sectional view taken along the line marked II-II of the apparatus in Figure 1 ;

Figure 3 is a schematic cross-sectional view of the apparatus according to the invention interposed between means of feeding particles of wooden material and a mixer.

Ways of carrying out the Invention

With reference to the figures, the reference numeral 1 generally indicates an apparatus for injecting chemical components into a flow of loose wooden material.

In particular, the apparatus 1 can be used in order to achieve the pre- mixing of adhesive substances and additives in general with particles (chips, shavings, fibers etc.) of wooden material in plants for producing panels of chipboard, MDF (Medium Density Fibreboard), OSB (Oriented Strand Board) and the like.

The apparatus 1 comprises a tubular body 2 that extends along a longitudinal axis A, is provided with at least one inlet 3 and with at least one outlet 4 and is crossed internally by a flow of loose wooden material, represented by the arrow indicated with the letter F in the figures, from the inlet toward the outlet.

Under operating conditions, the apparatus 1 is positioned with its longitudinal axis A not horizontal, and preferably vertical, so that the inlet 3 is arranged above the outlet 4 and the flow F crosses it by falling as a result of the force of gravity.

Also, the apparatus 1 is designed to be installed with the inlet 3 connected to the outlet of conventional means of feeding loose wooden material, of the type of a conventional dosage apparatus D, not described in detail, and the outlet 4 connected to the inlet of a mixer M of a known type, which is also not described in detail.

The apparatus 1 comprises, furthermore, means 5 for injecting at least one chemical component toward the flow F of loose wooden material, which are supported by and inside the tubular body 2.

In particular, the injection means 5 include at least one injector nozzle 6 supported by the inner wall 7 of the tubular body 2, preferably in proximity to the inlet 3 and directed toward the longitudinal axis A, The injection means 5 include, moreover, a system for feeding the at least one chemical component to be distributed in the flow F of loose wooden material, which is not described in detail.

In the embodiment shown, the injection means 5 include a plurality of nozzles 6 (of which only two are shown) distributed along a section of the tubular body 2 at right angles to the longitudinal axis A in proximity to the inlet 3, but alternative arrangements of the nozzles 6 are not excluded.

The apparatus 1 comprises, furthermore, scraper means 8 which are associated with the internal wall 7 and can move tangentially with respect to it in order to clean it from any deposits of chemical component and means 9 for actuation with a relative motion of at least one of the tubular body 2 and the scraper means 8 with respect to each other.

These actuation means 9 preferably operate continuously so as to perform the cleaning over the entire operation of the apparatus 1 and to prevent the buildup of solid deposits of non-negligible size on the internal wall 7 which, occasionally introduced into the mixer M, could give rise to the formation of lumps in the paste being processed. Alternatively, the actuation means 9 could function intermittently and be activated on command by an operator.

The scraper means 8 include at least one spatula 10 which is positioned substantially in contact with the internal wall 7 and can move tangentially with respect to it so as to scrape at least a portion thereof. The phrase "substantially in contact" is intended to mean that the spatula 10 can be positioned directly in contact with the internal wall 7 or be kept spaced therefrom by a minimal gap (of the order of a few tenths of a millimetre) according to the requirements of the application.

Preferably, the scraper means 8 include a plurality of spatulas 10.

If the tubular body 2 has an axially symmetrical shape with respect to the longitudinal axis A, then the actuation means 9 actuate the rotation of at least one of the tubular body 2 and the spatulas 10 about the longitudinal axis A.

In the embodiment shown, the tubular body 2 has a frustum-shaped configuration that tapers toward the outlet 4 so as to define a common hopper and the scraper means 8 comprise a supporting structure for three spatulas 10, each of which are mutually angularly spaced by 120° and lie along respective generatrices of the tubular body 2. The supporting structure includes two rings, an upper ring 11 and a lower ring 12, which are rigidly connected to the spatulas 10. The possibility is not excluded of connecting the spatulas 10 to the rings 11 and 12 via the interposition of elastically yielding elements so as to prevent shocks from occurring should the spatulas 10 encounter deposits of chemical components on the internal wall which resist the detachment action.

The spatulas 10 extend downstream of the nozzles 6, in the direction in which the tubular body 2 is crossed by the flow F of loose wooden material, up to the vicinity of the outlet 4.

The actuation means 9 are constituted by an electric motor 13, supported externally by the tubular body 2, for the actuation in rotation, about a vertical axis, of a pinion 14 engaged by a first annular element 15 with internal toothing, which is arranged perpendicular to the longitudinal axis A and is rigidly connected to the upper ring 11. A second annular element 16 is also provided, which is rigidly connected to the tubular body 2 and is arranged externally to the first annular element 15. Between the first and the second annular element, respectively, 15 and 16, rolling elements 17 are interposed so as to constitute a form of bearing. The first annular element 15 is, therefore, freely rotatable about the longitudinal axis A with respect to the second annular element 16 and with respect to the entire tubular body 2.

The possibility is not excluded that the actuation means 9 can also actuate the tubular body 2 in rotation about the longitudinal axis A, in the opposite direction with respect to the scraper means 8.

It is in any case possible to have different shapes of the internal wall

7, for example cylindrical in type and such as to define cross-sections through the longitudinal axis A which are polygonal in shape. In this last case the scraper means 8 can move with respect to the tubular body 2 with an alternating translational motion tangentially to at least one of the faces that form the wall itself. Advantageously, the apparatus 1 can comprise cooling means 18 which are associated with the internal wall 7 and/or with the scraper means 8 so as to achieve a temperature of the corresponding surfaces that is substantially lower than the temperature of the flow F of loose wooden material. Preferably, the temperature of these surfaces is kept at a value that is close to the condensation temperature of the humidity carried by the flow F and/or of the surrounding environment. In this way the condensation of part of the humidity is caused so as to achieve the formation of a thin film of condensate on the cooled surfaces. This effect reduces the adhesive power of the chemical components, and particularly of thermosetting glues, on the internal wall 7 thus facilitating the cleaning with the scraper means 8 and it also makes it possible to keep the spatulas 10 clean.

The cooling means comprise at least one chamber 18 for the passage of a cooling fluid, such as water, the chamber 18 being associated with the surface to be cooled.

In the embodiment shown, cooling means 18 are provided exclusively for the internal wall 7, and the chamber 18 is defined by an interspace formed within the thickness of the tubular body 2 and is annular in shape.

In another embodiment, which is not shown, there can be, as an alternative to or in addition to the foregoing, means of cooling the scraper means 8 so as to achieve a temperature of the surfaces of the spatulas 10 which is lower than that of the flow F of loose wooden material and, preferably, close to the condensation point of the humidity contained therein. In detail, these cooling means can include a chamber for the passage of a cooling fluid which is formed within the spatulas 10 and a system for supplying the fluid which can move with the scraper means 8. In this way it is possible to prevent the formation of deposits of chemical components on the spatulas 10 as well.

The operation of the apparatus of the present invention is as follows. The loose wooden material is dosed and released by the feeding means D at the inlet 3. As a result of the force of gravity the loose wooden material longitudinally crosses the tubular body 2, exits from the outlet 4 and enters the mixer M. During the crossing of the tubular body 2 the injection means 5 distribute, into the flow F of loose wooden material, preset quantities of one or more chemical components, such as adhesives and additives.

The mechanical action of the scraper means 8 assisted by the effect produced by the cooling means 18, which inhibit the adhesion of chemical components, particularly of the thermosetting type, to the internal wall 7, make it possible to keep it clean, thus ensuring the efficiency of the entire manufacturing process, without performance of extraordinary maintenance.

Indeed, the continuous removal of any deposits of chemical components from the internal wall 7 prevents the buildup of lumps that might not be homogenised by the mixer M with consequent formation of manufacturing discards.

In practice it has been found that the invention as described achieves the set aim and objects and, in particular, attention is drawn to the fact that the apparatus according to the invention ensures a correct distribution of the chemical components in the flow of loose wooden material, prevents the formation of manufacturing discards, and does not require periodic maintenance.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

Moreover, all the details may be substituted by other, technically equivalent elements.

In practice the materials employed, as well as the contingent dimensions and shapes, may be any according to requirements, but without for this reason extending beyond the scope of protection of the following claims. The disclosures in Italian Patent Application No. MO2010A000132 from which this application claims priority are incorporated herein by reference,

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.