WO2010004120A1

WO2010004120A1 - Device for producing a dry stream of solid particles and particle size analyzer comprising such a device

Info

Publication number: WO2010004120A1
Application number: PCT/FR2009/000790
Authority: WO
Inventors: Georges Philippe; José DA CRUZ; Dominique Sornin-Petit; Xavier Gilbert
Original assignee: Compagnie Industrielle Des Lasers Cilas
Priority date: 2008-07-01
Filing date: 2009-06-25
Publication date: 2010-01-14
Also published as: FR2933314A1; FR2933314B1

Abstract

Device for producing a dry stream of solid particles and particle size analyzer comprising such a device. According to the invention, said device (2) comprises an electrical vibrator (3) powered by an AC voltage (Va), the frequency and the duty cycle of which can be continuously adjusted.

Description

Device for producing a dry flow of solid particles and granulometer comprising such a device.

The present invention relates to a device for producing a dry flow of solid particles. Although not exclusively, the device of the invention is particularly suitable for use in solid particle dry particle granulometers.

Such a device is already known comprising: a bowl containing a reserve of said particles; an electric vibrator, adapted to vibrate said bowl to obtain a current of said particles flowing out of said bowl; and means for generating a gaseous stream into which said stream of particles is introduced to form said dry stream of particles.

In such a known device, said electric vibrator is powered from the local distribution network and the only parameter available to the operator for adjusting the density of the particles in said dry stream is the supply voltage. It sometimes results that said density can not be uniform and reach a predetermined value. It even happens that, in this known device, it is impossible to form the current of said particles. The present invention aims to overcome these disadvantages.

To this end, according to the invention, the device, of the type mentioned above, improved to allow the realization of a dry flux of solid particles with predetermined uniform density, is remarkable in that: - said vibrator is powered by a AC voltage, whose frequency and duty cycle are adjustable; and said device comprises means for continuously adjusting said frequency and said duty cycle, so as to obtain said predetermined uniform density. Thus, not only can the device according to the invention be used without modifications depending on the voltage and the frequency of the local distribution network, but it also provides the operator with two adjustment parameters (the frequency and the duty cycle). enabling it to obtain a uniform particle density and to continuously adjust this density to a desired value. This adjustment can be made either by adjusting only one of the two adjustment parameters, or by modifying each of the two parameters (simultaneously or not), using the corresponding adjustment means. These two adjustment parameters thus make it possible to find the best tuning of the frequencies of the system, in order to optimize the flowability of the powders.

Of course, these two adjustment parameters can be supplemented by a third constituted by an adjustable amplitude for said AC voltage. This alternating voltage may consist of a sequence of alternately positive and negative pulses. Such pulses may be in the form of rectangular or square slots. In the latter case, the device may advantageously comprise a switching power supply. In order to further improve the efficiency of the device according to the invention, it is advantageous that the latter comprises means capable of varying the flow rate of said particle stream before introduction into said gaseous jet. Said operator then has at his disposal a fourth parameter (said flow) to obtain a predetermined uniform density. According to another characteristic of the invention, said bowl comprises, in known manner, a conical bottom falling towards the periphery and a lateral opening, which is arranged facing the lowered peripheral portion of said bottom and through which said particle stream flows. , and, according to the invention, said means capable of varying the flow rate of said flow of particles before introduction into said jet gas advantageously comprise an inner sleeve containing said particles and mounted movably within said bowl to be able to approach said bottom, to contact, or away from it. Thus, the flow rate of the solid particle stream out of said bowl can be adjusted continuously precisely, manually or automatically, to obtain a particle flow rate that provides the desired particle density.

Advantageously, the device comprises means for supporting said inner sleeve provided with: means for adjusting the spacing of the lower part of said sleeve relative to the conical bottom of said bowl, so as to adjust the flow rate of said stream of solid particles out of said bowl ; and fixing means in position of said sleeve, adapted to fix the latter after adjustment of said spacing.

Advantageously, said spacing adjustment means comprise a support comprising a recess, of cylindrical shape, whose internal lateral wall is threaded and said fixing means comprise clamping jaws able to be clamped by at least one screw of Tightening. Said sleeve then comprises a threaded collar disposed on its side wall and adapted to cooperate with the threaded inner side wall of said recess.

Thus, it is possible to finely adjust and fix the spacing of the sleeve relative to the conical bottom of the bowl, so as to precisely adjust the flow rate of the stream of solid particles out of said bowl.

The present invention also relates to a particle size analyzer for determining the size of solid particles distributed in a dry stream of such particles. According to the invention, said granulometer, comprising at least one at least substantially monochromatic light beam illuminating said stream, is remarkable in that it comprises the device for producing a solid particle dry stream as specified above. The figures of the appended drawing will make it clear how the invention can be realized. In these figures, identical references designate similar elements.

FIG. 1 is a diagrammatic overall view, in perspective, of an exemplary embodiment of the granulometer according to the present invention.

FIG. 2 is a schematic view in partial cross-section of the device for producing a solid particle dry flow according to the invention belonging to the particle size analyzer of FIG. 1.

FIG. 3 presents a diagram of the variations, as a function of time t, of an example of alternating voltage Va delivered by the power supply of the device represented in FIG. 2.

FIG. 4 is a partial longitudinal section of the ejection tube and the suction tube of the granulometer illustrated in FIG.

According to the invention, as shown in FIG. 1, the granulometer I comprises a device 2 for producing a dry flux of solid particles with a predetermined uniform density.

As illustrated in FIGS. 1 and 2, the device 2 of the invention comprises an electric vibrator 3 powered by an alternating voltage Va constituted, in the example represented in FIG. 3, by a succession of alternately positive pulses and negative in the form of rectangular or square slots.

Advantageously, this AC voltage Va (see FIG. 3) is delivered by a switching power supply 4. It is thus possible to vary continuously (before making a measurement with the particle size analyzer and / or during such a measurement) the frequency and / or the duty cycle of the voltage delivered by the power supply 4.

The adjustment of the frequency 1 / T and / or the duty cycle a / b of the voltage Va can be carried out manually by an operator, for example by means of adjustment buttons 5A and 5B, respectively shown in FIG. Alternatively, it can be performed automatically by means of a servo circuit (not shown in the figures).

The adjustment knob 5A of the frequency 1 / T can be manipulated either independently or in combination with the adjustment knob 5B of the duty cycle a / b.

As shown in the diagram of FIG. 3, in the case of a square voltage Va of period T and a duty cycle equal to 50% (the duration a and b of the positive and negative states being equal, with T = a + b ), an increase in the duty cycle at constant frequency results in an increase in the duration of the positive state (equal to a ') and a reduction in the duration of the negative state (equal to b'). We thus have a '> b' and T = a '+ b' = a + b.

As illustrated in Figure 2, the vibrator 3 comprises a vibrating assembly 6 on which is fixed a bowl 7 of cylindrical shape. The bowl 7 has a conical bottom δ lowering towards the periphery and a lateral opening 9 which is arranged facing the peripheral portion lowered from said bottom 8. The lateral opening 9 of the bowl 7 makes it possible to place the bowl 7 in communication with a flow ramp 10, one end 1 1 is fixed on the side wall 12 of said bowl 7 and another end 13 cooperates with a vertical feed gutter 4 of cylindrical shape.

In addition, an inner sleeve 15, containing solid particles P, is movably mounted inside said bowl 7 to be able to approach the conical bottom 8, until contact, or away from it. The inner sleeve 15 is held suspended inside the bowl 7 by means of support means 16.

The support means 16, attached to a fixed mast 17, has, on the one hand, adjustment means 18 of the spacing e of the lower part of the sleeve 15 relative to the conical bottom 8 of said bowl 7 and, of on the other hand, means 19 for fixing the sleeve 15 in position.

According to the embodiment shown in FIG. 2, the adjustment means 18 comprise a flat support 18a in which a cylindrical recess has been made. The inner side wall 18b of said recess is threaded so as to co-operate, with adjustment, with a threaded collar 20 disposed on the side wall of said sleeve 15. Thus, it is possible to finely adjust the spacing e so as to precisely adjust the output flow rate. solid particles P of the sleeve 15 in the bowl 7 and, consequently, the flow rate of the stream of solid particles poured into the ramp 10. The fastening means 19 are, in turn, constituted by clamping jaws 19a that can be closed. by a clamping screw 19b so that when the output rate of the solid particles is adjusted, the operator can block the position of the sleeve 15 by tightening the clamping screw 19b. The vibrations applied to the bowl 7 allow the movement of solid particles from the inner sleeve 15, for example in the opposite direction of clockwise. When the stream of solid particles arrives at the lateral opening 9 of the bowl 7 through which it leaves, it is distributed regularly in the ramp 10, then advances along it with a quasi-constant flow up to The flow gutter 14. The particle flow rate in the gutter 14 can be continuously monitored using the two adjustment parameters (frequency 1 / T and duty cycle a / b) associated with the AC voltage. Goes supplying said vibrator, as well as by the spacing e and, possibly, by the amplitude of the pulses of said voltage.

The supply channel 14 then makes it possible to supply solid particles with an ejector 21, comprising a venturi (not shown), connected on one side to a pressurized air inlet 22 and on the other side to a tube of ejection 23 described later. The ejector 21 is capable of generating a jet of air at high speed into which the flow of solid particles is introduced, so as to form the dry flow of solid particles thrown into the ejection tube 23. In addition, the tube ejection 23, of cylindrical shape and longitudinal axis XX, which receives the dry stream of solid particles, allows the creation of a dry stream 24 of solid particles of cylindrical shape and homogeneous density.

As shown in FIGS. 1 and 4, the suction tube 25 has two openings 26, facing each other, formed in the side wall 27 of the tube 25. These openings 26 allow the dry flow 24 to be traversed by a beam 28 of monochromatic light generated by a laser generator 29 of longitudinal axis YY, for example orthogonal to the axis XX. The suction tube 25 is also equipped, at its unobstructed end 30, with a powerful industrial vacuum cleaner (not shown) activated, for example, after a granulometry measurement is made on the dry stream 24 of solid particles.

A set 31 of photosensitive detectors is provided downstream of the suction tube 25 (with respect to the direction of propagation of the laser beam 28), so as to observe the diffraction-diffusion pattern formed by the beam 28 of the laser generator 29 after the crossing the dry stream 24.

A protective window 32 is further interposed between the suction tube 25 and the detector assembly 31, orthogonal to the axis YY. Moreover, a cleaning nozzle 33, connected to a compressed air circuit (not shown) controlled by a solenoid valve, is arranged in the vicinity of the protective window 32. At the end of a granulometry measurement, after activation of the aspirator of said suction tube 25, the solenoid valve can open, allowing the cleaning nozzle 33 to blow air at high speed on the protective window 32, to drive out the particles stuck on this last.

Claims

1. Device for producing a dry flux of solid particles with a predetermined uniform density, device (2) comprising: a bowl (7) containing a reserve of said particles; - An electric vibrator (3), able to vibrate said bowl (7) to obtain a stream of said particles flowing out of said bowl (7); and means (21) for generating a gaseous stream into which said stream of particles is introduced to form said dry stream of particles (24); characterized in that said vibrator (3) is powered by an alternating voltage (Va), whose frequency and duty cycle are adjustable; and in that said device (2) comprises means (5A, 5B) for continuously adjusting said frequency and said duty cycle, so as to obtain said predetermined uniform density.

2. Device according to claim 1, characterized in that said alternating voltage (Va) is constituted by a succession of alternately positive and negative pulses.

3. Device according to claim 2, characterized in that said pulses have the form of rectangular or square crenellations.

4. Device according to one of claims 1 to 3, characterized in that it comprises means adapted to vary the flow rate of said particle stream before introduction into said jet gas.

5. Device according to claim 4, wherein said bowl (7) has a conical bottom (8) lowering towards the periphery and a lateral opening (9), which is arranged facing the lowered peripheral portion of said bottom (8). ) and through which said stream of particles leaves, characterized in that said means adapted to vary the flow rate of said stream of particles before introduction into said jet gas comprises an inner sleeve (15) containing said particles and mounted movably inside said bowl (7) to approach said bottom (8), until contact, or away from it.

6. Device according to claim 5, characterized in that it comprises support means (16) of said inner sleeve (15) provided: adjusting means (18) of the spacing (e) of the lower portion of said sleeve (15) relative to the conical bottom (8) of said bowl (7), so as to adjust the flow rate of said stream of solid particles out of said bowl (7); and fixing means in position (19) of said sleeve (15), adapted to fix the latter after adjustment of said spacing.

7. Device according to claim 6, characterized in that said adjustment means (18) of the spacing (e) comprise a support (18a) comprising a cylindrical recess whose inner side wall (18b) is threaded; - in that said fixing means (19) comprise clamping jaws (19a) adapted to be clamped by at least one clamping screw (19b); and in that said sleeve (15) has a threaded collar (20) disposed on its side wall and adapted to cooperate with the internal threaded side wall (18b) of said recess.

8. Granulometer for determining the size of solid particles distributed in a dry flow of such particles, said granulometer (I) comprising at least one light beam (28) at least substantially monochromatic illuminating said flow (24), characterized in that it comprises the device (2) specified in any one of claims 1 to 7.