Method and apparatus for forming compacted powder products

Abstract

An apparatus for forming compacted powder products. The apparatus includes a powder supply system and a compacting station. An emitter emits an input X-ray beam having a predetermined emission intensity. An output detector detects an output parameter representing an output intensity of the X-ray beam which passes through the powders. A reference detector detects a reference parameter representing the effective intensity of the X-ray beam generated. A control unit is programmed to compensate the output parameter by means of the reference parameter and to generate a control signal representing the density detected and to control the powder supply system by means of the control signal.

Claims

1. A method for forming compacted powder products, comprising the steps of: a) depositing a soft powder mass on a supporting table and delivering the soft powder mass to a compacting station; b) compacting the soft powder mass against the supporting table to obtain the compacted powder product; c) generating on a first side of the powders an input X-ray beam having a predetermined emission intensity; d) detecting, on a second side of the powders, opposite the first side, an output parameter representing an output intensity of the X-ray beam, which passes through the powders; e) measuring a thickness of the powders and determining a density thereof as a function of the emission intensity, the output intensity, and the thickness and type of the powders, f) detecting on the first side the powders a reference parameter representing an effective intensity of the X-ray beam generated; g) compensating the output parameter using the reference parameter to determine the density of the powders; and h) generating a control signal representing a detected density and controlling the step of depositing the soft powder mass using the control signal.

2. The method according to claim 1, wherein the compensating step g) is performed by normalizing the output parameter to obtain a compensated parameter given by a ratio between the output parameter and the reference parameter.

3. The method according to claim 1, wherein the compensating step g) is performed by applying an algorithm which operates as a function of the effective hardness of the input X-ray beam determined as a function of the reference parameter.

4. The method according to claim 1, comprising a calibrating step in which a plurality of reference parameters and output parameters performing steps c)-f) on a plurality of powders of known density are stored.

5. The method according to claim 1, wherein steps c)-f) are performed on the compacted powder product.

6. The method according to claim 5, comprising controlling the step of compacting the soft powder mass using the control signal.

7. The method according to claim 1, wherein steps a) and b) are performed continuously and comprise: continuously depositing the soft powder mass on the supporting table which is slidable in a feed direction, in such a way as to form a continuous strip of powders, feeding the supporting table through a compacting station operating continuously to compact the powders as the supporting table advances in such a way as to obtain the compacted powder product in the form of a continuous belt by means of a sliding compacting surface.

8. The method according to claim 1, wherein steps a) and b) are performed discontinuously and comprise: depositing a quantity of soft powder mass and compacting it using a reciprocating press.

9. The method according to claim 1, wherein steps c)-f) are repeated at two or more points to determine a powder density profile.

10. A method for forming ceramic tiles comprising the method for forming the compacted powder products according to claim 1.

11. An apparatus for forming compacted powder products, comprising: a powder supply system configured to deposit a soft powder mass on a supporting table; a compacting station configured to receive the soft powder mass and to compact the soft power mass against the supporting table to obtain a compacted powder product; an emitter mounted on a first side of the powders and configured to emit an input X-ray beam having a predetermined emission intensity; an output detector mounted on a second side of the powders, opposite the first side, and configured to detect an output parameter representing an output intensity of the X-ray beam which passes through the powders; a measuring device configured to measure the thickness of the powders; a control unit operatively connected to the emitter, the output detector and the measuring device are programmed to determine the density of the powders as a function of the emission intensity, the output intensity, and the thickness and type of the powders; a reference detector mounted on the first side and configured to detect a reference parameter representing the effective intensity of the X-ray beam generated, wherein the control unit operatively connected to the powder supply system and to the reference detector and is programmed to compensate the output parameter by means of the reference parameter and to generate a control signal representing the density detected and to control the powder supply system by means of the control signal.

12. The apparatus according to claim 11, wherein the reference detector is located at a position not screened from the input X-ray beam and offset relative to the output detector.

13. The apparatus according to claim 11, wherein the control unit is programmed to perform compensation by normalizing the output parameter to obtain a compensated parameter given by the ratio between the output parameter and the reference parameter.

14. The apparatus according to claim 11, wherein the control unit is programmed to perform compensation by applying an algorithm which operates as a function of the effective hardness of the input X-ray beam determined as a function of the reference parameter.

15. The apparatus according to claim 11, wherein the emitter positioned in such a way as to operate on the compacted powder product.

16. The apparatus according to claim 11, wherein the powder supply system is configured to operate continuously on a supporting table which is slidable in a feed direction, in such a way as to form a continuous strip of powders and wherein the compacting station comprises a sliding compacting surface to continuously compact the powders as the supporting table advances to obtain the compacted powder product in the form of a continuous belt.

17. The apparatus according to claim 16, wherein the emitter, the output detector and the reference detector are movable in a direction transverse to the feed direction to determine a powder density profile.

18. The apparatus according to claim 11, wherein the compacting station comprises a reciprocating press operating on a quantity of soft powder mass.

19. An apparatus for forming ceramic tiles comprising an apparatus for forming compacted powder products according to claim 11.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

(1) With reference to the accompanying drawing, the numeral 1 denotes in its entirety an apparatus for forming compacted powder products 100.

(2) More specifically, the apparatus 1 illustrated in the drawing defines a continuous compacting line comprising a conveyor belt 2 defining with its upper active portion a slidable supporting table 3.

(3) The supporting table 3 is mounted horizontally and extends at least from an input portion 3a on which a soft powder mass “M” is deposited and an output portion 3b from which the products 100 are moved away.

(4) The conveyor belt 2 is motor-driven in such a way as to move the supporting table 3 in a feed direction 4 corresponding to a longitudinal direction of the apparatus.

(5) The mass “M” is deposited on the supporting table 3 by means of a powder supply system 5. In the embodiment illustrated, the powder supply system is configured to operate continuously on a supporting table 3 which is slidable in the feed direction 4, in such a way as to form a continuous strip of powders.

(6) In a possible embodiment, of which the accompanying drawing constitutes a non-limiting example, the powder supply system 5 comprises a dispensing device 6 provided with a dispensing mouth 7 configured to create a loading profile which is variable both in the feed direction 4 and in a direction transverse to the feed direction 4 in the horizontal plane of the conveyor belt.

(7) The dispensing mouth 7 may, for example, be embodied according to what is described and illustrated in EP2050549, incorporated herein by reference, comprising a barrier 8 provided with a shaped levelling profile made preferably of compliant elastomer. The barrier may be shaped according to requirements and fixed in the new configuration by operating manually on tightening screws or on suitable automatic systems (for example, electronically controlled hydraulic actuators).

(8) In a possible embodiment, the dispensing mouth 7 is configured to skim the mass “M” in such a way as to obtain a constant level. For example, electromechanical or pneumatic actuators can be driven to adjust the dispensing mouth 7, in particular the barrier 8.

(9) In addition or alternatively, the loading profile may be controlled, through algorithms and drive systems, by a series of digital actuators not illustrated (for example, electrovalves, pistons, gate valves, etc.).

(10) In addition or alternatively, the powder supply system 5 comprises a selective removal device 9 and/or an accumulating device 10.

(11) The selective removal device 9 is configured to locally reduce quantities of powder (for example, by means of suction nozzles) and may be made, for example, as described and illustrated in EP1594666B1, which is incorporated herein by reference, where one suction nozzle operates uniformly on the full loading width and performs selective reduction by means of dividers, such as actuator-driven gate valves.

(12) The accumulating device 10 is configured to locally deliver small additional quantities of soft powder. An example of an accumulation device is described and illustrated in WO2009/118611A1, which is incorporated herein by reference, comprising a container hopper, a distribution element and vibrator means configured to set the distribution element in vibration. The soft mass “M”, suitably modulated in height (both transversely and longitudinally) is made to advance up to a compacting station 11 configured to receive the soft mass “M” and to compact it against the supporting table 3 to obtain the product 100.

(13) In one embodiment, as for example illustrated in the accompanying drawing, the apparatus 1 comprises a continuous compacting station 11 comprising converging belts 12 defining a sliding compacting surface 13 which is flexible and placed over the supporting table 3. The sliding compacting surface 13 slides in the same direction as the feed direction 4 of the supporting table 3. Also provided are pressing rollers 14 configured to press the compacting surface 13 towards the supporting table in such a way as to press the soft mass “M” which is interposed between them.

(14) The sliding compacting surface 13 continuously compacts the powders as the supporting table 3 advances in such a way as to obtain the compacted powder product 100 in the form of a continuous belt.

(15) The compacted product in the form of a continuous belt feeding out of the compacting station 11 is cut and trimmed by cutting devices 15. The products are carried on rollers 16 moving in the feed direction 4 towards further processing stages of the production cycle (drying, decorating, firing, cutting to size and surface finishing).

(16) Downstream of the compacting station 11, the products 100 meet an inspection and measuring system 17 configured to measure the density of the material non-destructively.

(17) The inspection and measuring system 17 comprises an emitter 18 mounted on a first side 19 of the powders (more specifically, of the product 100) and configured to emit an input X-ray beam having a predetermined emission intensity I.sub.0.

(18) The inspection and measuring system 17 comprises an output detector 20 mounted on a second side 21 of the powders, opposite the first side 19, and configured to detect an output parameter representing an output intensity I.sub.1 of the X-ray beam which passes through the powders.

(19) The inspection and measuring system 17 comprises a measuring device 22 configured to measure the thickness of the powders and, more specifically, of the product 100.

(20) The inspection and measuring system 17 comprises a reference detector 23 mounted on the first side 19 and configured to detect a reference parameter representing the effective intensity I.sub.2 of the X-ray beam generated.

(21) Preferably, the reference detector 23 is located at a position not screened from the input X-ray beam and offset relative to the output detector 20.

(22) A control unit 24 is operatively connected to the emitter 18, the output detector 20, the measuring device 22 and the reference detector 23 and is to programmed to determine the density of the powders as a function of the emission intensity I.sub.0, the output intensity I.sub.1, and the thickness and type of the powders.

(23) More specifically, the control unit 24 processes signals from the emitter 18, from the output detector 20 and from the reference detector 23 to generate an X-ray absorption signal. The control unit 24 also processes a signal from the measuring device 22 and, taking into account the thickness measured, determines the density of the material by applying the Lambert-Beer law.

(24) Further, in determining the density of the material, the control unit 24 is programmed to compensate the output parameter by means of the reference parameter.

(25) Moreover, the control unit 24 is programmed to generate a control signal “S1” representing the density detected.

(26) The control unit 24 is connected to the powder supply system 5 to control it as a function of the control signal S1.

(27) In one embodiment, the control unit 24 is connected to the compacting station to control it as a function of the control signal S1 (in addition or alternatively to controlling the powder supply system 5).

(28) The control of the supply system consequently modifies the loading profile of the soft mass “M”. For example, the dispensing device 6 comprises a dispensing mouth 7 whose shape can be modified as a function of the control signal “S1”. In particular, electromechanical or pneumatic actuators can be driven as a function of the control signal “S1” to modify the barrier 8. The control signal “S1” may also be used to control the selective removal device 9 and/or the accumulating device 10.

(29) Optionally, the control unit 24 is programmed to generate a control signal “S2” representing the density detected and to control the compacting station 11, in particular the pressing rollers 14, by means of the control signal “S2”.

(30) Advantageously, the emitter 18, the output detector 20 and, if necessary, the reference detector 23, may be mounted on units which are movable on guides extending transversely to the feed direction 4, and which are controlled by the control unit 24 which controls their movement in such a way as to determine a density profile transversely to the product 100.

(31) Advantageously, each point of the profile is given by the average of a plurality of closely consecutive readings taken in a predetermined length of time (e.g., 1 sec). That way, it is possible to measure products whose top surface is irregular (textured).

(32) During the production of products, in particular ceramic slabs, the inspection and measuring system 17 continuously monitors the density of the material, preferably by accumulating information in the form of density profiles. This information is then sent by way of the control signal “S1” to the powder supply system 5 upstream of the compacting station, which adjusts the loading profile accordingly, and if necessary, by way of the control signal “S2” to the compacting station 11.

(33) Thanks to the reference detector 23, it is possible to automatically compensate any fluctuations of intensity and/or hardness of the X-ray beam. The reference detector 23 is irradiated by the same source, that is, by the emitter 18, and is located at a point where it is not screened. Thus, the time variations measured with the reference detector 23 are those attributed to the fluctuations of the X-ray beam emitted and may thus be compensated.

(34) Compensation may occur at different levels. For example, the control unit 24 may be programmed to perform compensation by normalizing the output parameter to obtain a compensated parameter given by the ratio between the output parameter and the reference parameter. Alternatively, the control unit 24 may be programmed to perform compensation by applying an algorithm which operates as a function of the effective hardness of the input X-ray beam determined as a function of the reference parameter.

(35) The apparatus described above allows the density to be measured to continuously and in real time, making it possible to obtain a density profile and feedback control of the powder supply system and, if necessary, of the compacting station.

(36) The foregoing can also be applied to a traditional forming apparatus operating with reciprocating presses, where feedback may operate on the loading systems and/or on the devices for metering the additional powders. In this case, operation is discontinuous and involves depositing a quantity of soft powder mass and compacting it with a reciprocating press.

(37) In both cases, alternatively to what is described, the inspection and measuring system 17 may be located upstream of the compacting station and configured to measure non-destructively the density of the soft mass “M”.

(38) In both cases, the apparatus in use operates using a method for forming compacted powder products wherein a soft powder mass “M” is deposited on a supporting table and delivered to a continuous compacting station or to reciprocating presses.

(39) The soft mass “M” is compacted against the supporting table 3 to obtain the compacted powder product. Before, or preferably after compaction and hence with reference to the compacted powder product, an input X-ray beam having a predetermined emission intensity I.sub.0 is generated on the first side of the powders. The beam passes through the mass, in particular through the product, making it possible to detect, on a second side of the powders, opposite the first side, an output parameter representing an output intensity I.sub.1 of the X-ray beam which passes through the powders. Also, the thickness of the powders is measured and the density thereof is determined as a function of the emission intensity, the output intensity, and the thickness of the powders by applying the Lambert-Beer law.

(40) By detecting on the first side of the powders, a reference parameter representing the effective intensity I.sub.2 of the X-ray beam generated, it is possible to compensate the output parameter using the reference parameter to determine the density of the powders.

(41) The actions described above can be repeated at two or more points to determine a powder density profile.

(42) Lastly, a control signal “S1” and/or “S2” representing the detected density is then generated in order to control the step of depositing the soft powder mass using the control signal “S1” and, if necessary, the step of compacting the soft powder mass using the control signal “S2”.

(43) The method may also comprise a calibrating step in which a plurality of reference parameters and output parameters operating on a plurality of powders of known density are stored.

(44) Both the method and the apparatus described above refer both to powder compaction in general and to its specific application in the sector of ceramic tiles in the context of a method and an apparatus for forming ceramic tiles.