WO1992001209A1

WO1992001209A1 - Process, device and installation for the volumetric dosing of a powder product with compacting

Info

Publication number: WO1992001209A1
Application number: PCT/FR1990/000511
Authority: WO
Inventors: Dominique Gavotto
Original assignee: Adl Automation
Priority date: 1989-01-06
Filing date: 1990-07-05
Publication date: 1992-01-23
Also published as: FR2641862B1; FR2641862A1

Abstract

Dosing of powder products. The device is characterized in that: the attachment body defines a chamber (7) connected to a pressurization-depressurization circuit (17); the guided piston (8) slides in the chamber (7) and is extended by a tubular rod (9) opening into the chamber (7), said rod being in sliding engagement in the pipe (10), thereby constituting its core, and carrying at its end the pellet (12). Application for the production of pyrotechnic cartridges.

Description

METHOD, DEVICE AND INSTALLATION FOR THE VOLUMETRIC DOSING OF POWDERED PRODUCT WITH COMPACTION

TECHNICAL AREA :

The present invention relates to the dosing of pulverulent products and, more particularly, of powder used as such and alone or in combination with other products for various varied applications and, more especially, for the manufacture of cartridges with pyrotechnic effect.

PRIOR TECHNIQUE:

To dose products such as above, two techniques are generally used.

One, called mass dosing, involves taking into account the mass of the pulverulent product to measure the weight to be imparted at a determined dose which is deemed to be measured when the defined weight is reached. Another method is called volumetric dosing because of its principle of taking into account only the filling of a standard capacity whose volume corresponds to that of the desired dose. As a general rule, this second method is often preferred, especially for small doses, because of its greater flexibility, ease of execution and the use of less sophisticated equipment than that implied by the simple or double weighing method.

In the application to the above field, the volumetric dosage poses, however, a certain problem whose acuity increases in inverse ratio to the volume to be measured.

The quality of a volumetric dosage and its repeatability over time are linked to the precision of the volume selected by the dosing device. The accuracy of a mass determined by volumetric dosing necessarily takes into account the density factor of the product to be dosed. So that the volume-mass ratio of a dose is as constant as possible in volumetric dosing, it is therefore essential that the density of the product is also as constant as possible.

Powdered products have the characteristic of being sensitive to storage, transport or handling conditions and of being subject to lump formation, arching effect or local compaction which vary significantly the local density. of the product sampled.

Whatever volumetric dosing system is used, such density variations cannot be controlled a priori. The control of the volume-mass ratio in such a case involves, a posteriori, the appreciation of the mass of powdered product dosed with, as a consequence, the recognition of the fact that a distributed dose can therefore be good or bad depending on the case. and subsequently influence the repeatable quality of the products or the conduct of a subsequent implementation process.

The unpredictable density variation of a powdered product dosed volumetrically in small quantities also has drawbacks when the system used for volumetric dosing involves a metering device with a vertical sucking tube. In general, such a type of dispenser is constituted by a tube comprising an adjustable bottom making it possible to define a capacity or metering chamber of adjustable volume which can be filled with pulverulent product after having plunged the tube into the reserve of product and exerted a suction. by The adjustable bottom. The suction is always based on a vacuum effect of constant value whose effect on a product whose density can vary results in an irregular filling of the metering chamber arranged to receive it. Assays carried out according to this principle experience distortions in the volume-mass ratio which are generally outside an acceptable range. The variations in density which may be presented by a pulverulent product also induce drawbacks during the evacuation of the aspirated dose. Indeed, the presence of lumps can lead to the formation of arch effect or clogging in the chamber which may not be completely emptied during discharge by blowing.

The variation in unpredictable density of the product can also be the cause of secondary drawbacks developing during blow-off which can cause, for example in the event of a density of the product lower than that expected, a local spraying effect. responsible for pollution of metering or receiving equipment.

The present invention aims to remedy the above drawbacks by proposing a new volumetric dosing method for powdered product which provides for implementing, simultaneously, a compacting phase of said product, so as to have a possibility of quick and easy measurement. a volumetric dose capable of presenting a precise and reproducible volume-mass ratio, whatever the unknown state of the pulverulent product sampled by suction.

The object of the invention is also to propose a new volumetric dosing technique which can be implemented in a practical, reliable manner and at an attractive cost price to provide, at high rate, doses of a pulverulent product having a precise and repeatable volume-mass ratio, whatever the density variations that the powder product to be dosed may present.

PRESENTATION OF THE INVENTION:

To achieve the above objectives, the volumetric dosing process for powdered product with compaction, including the steps of: a) - implementing an open tubular rod provided internally with a core, b) - controlling the removal of the core to a predetermined axial distance to define, inside the rod, _u, ιe dosing and compacting chamber, c) - engage in a supply of substance close to the andup bottom of this reserve the open tubular cane, d) - suck, during c), by the sliding core a dose of powdery product to fill the chamber, is characterized in that it then consists of: e) - ordering a first partial advance of the core to compact the dose against the bottom of the reserve and form a block of product compacted in the chamber, f) - extract the cane from the reserve, g) ~ order a second partial advance of the soul to reduce the chamber to the desired height and partially remove the block from the open end of the cane, h) - level the part of the protruding block out of the cane, i) - and control the total advance of the core to eject the leveled block into a container responsible for receiving it. The invention also relates to a volumetric metering device for powdery product, characterized by:

- a tubular rod open at its ends and extending an adaptation body delimiting a cavity communicating with a pressure-depression circuit, - a compacting piston guided in the cavity and extended by a tubular rod opening in the cavity , slidably engaged in the cane for which it forms a core, closed at its end by a porous pellet and capable of delimiting in the cane a metering chamber with variable volume,

- means for actuating the compacting piston in the straight stroke Set alternating line, - and means for cyclically controlling the operation of the pressure-depression circuit. The invention also relates to a volumetric metering installation involving at least one device as above.

Various other characteristics will emerge from the description given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments of the object of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional elevation of a volumetric metering device according to the invention. Figs 2 to 4 are sectional elevations illustrating the device of f g. 1 in different characteristic positions.

Fig.5 is a sectional elevation, partially broken away, showing a possibility of making an installation for the implementation of the method.

BEST WAY TO IMPLEMENT THE INVENTION:

The volumetric dosing device for powdery product for carrying out the process in accordance with

The invention consists of a support base 1 allowing the adaptation of the device to any suitable fixing means in connection with a metering installation. It can therefore be, indif erently, a movable or fixed tray intended to be superimposed on a fixed or movable table carrying, on the one hand, the container in which a dose of powder must be deposited and, on the other hand On the other hand, a reserve of powdery product or powder from which the dose must be taken.

In any case, it should be considered that, generally. The device, designated as a whole by the reference I, is superimposed on a lower activity zone II corresponding either to the removal of the pulverulent product, or to its deposit in the container.

The base 1 supports an adaptation body 2 made of any material suitable for presenting centering and adaptation means in relation to complementary means offered by the base 1. Such means can be, for example, centering cylindrical 3 formed between the body 2 proper and a also cylindrical nose 4 that the latter forms. The adaptation of the centering 3 and of the nose 4 is provided in complementary housings of the base 1 with interposition of seals 5 the function of which follows from the following. Preferably, the nose 4 is provided to completely cross the base 1, in order to be directed towards the zone II. The adapter body 2 internally delimits a guide cylinder 6 communicating with a cavity 7 which is formed inside the nose 4. The guide cylinder 6 and the nose 7 are intended to allow the mounting and guiding of a piston 8, called compaction, because of the function it assumes. The piston 8 is extended, in its part sliding in the cavity 7, by a tubular rod 9 sliding inside a also tubular rod 10 extending the nose 4. The rod 9 forms a tubular core for the rod 10 and has a length such that, in a position of maximum withdrawal of the piston 8, its end delimits, inside the rod 10, a chamber 11 called metering and precompaction. The rod 9 is closed, at its terminal end, by a porous pellet 12 and communicates, by its other end, with the cavity 7, either directly or indirectly by a radial hole 13 formed in the compacting piston 8. The cavity 7 is in relation, by one or more holes 14, with a recess 15 which is delimited between the nose 4 and the support base 1. The recess 15 communicates with an internal conduit 16 formed in the base to be connected to a circuit 17 pressure-depression controlled by means 18 of programmable cyclic operation. The seals 5 described above are used to isolate the recess 15 putting the cavity 7 in permanent communication with the circuit 17.

The device also comprises means 20 for actuating the compacting piston 8 in straight travel. Alternative line set inside the cylinder 6. These means 20 can be constituted in several suitable ways, one of which is illustrated, of preferred but not limiting, in FIG. 1. According to this figure, the means 20 comprise, first of all, a spring 21, for example of the helical type working under compression, interposed between the compacting piston 8 and a cap 22 closing the cylinder 6 while being adapted on the body 2. The spring 21, maintained under initial prestressing, is responsible for the displacement of the compacting piston 8 in the direction of the arrow f-, that is to say corresponding to the advance of the rod or core 9 to 1 inside the rod 10, from the reference position illustrated by La f g. 1.

The means 20 furthermore comprise a control means 23 antagonistic to the spring 21 and disposed in a cylinder 24 which delimits the cap 22. The means 23 can be constituted by a pneumatic cylinder with single or double effect, if necessary, being formed by the piston 8 or, preferably, by a metering piston 25 dt placed in the cylinder 24.

According to a preferred embodiment, the piston 25 is produced in a tubular manner so as to be threaded onto the compacting piston 8 and to be guided by cooperating with the cylinder 6 and the cylinder 24 which has a cross section greater than that of the cylinder 6. The piston 25 has, consequently, a head 26 which delimits, in the cylinder 24 and with the body 2, a chamber 27 with variable volume which is in relation, by a passage 28, with a circuit 29 supplying a fluid under pressure, by example of compressed air. The supply of the chamber 27 has the consequence of immobilizing the piston 25 in the high position against the action of an opposing control means 30 capable of pushing said piston in the opposite direction towards the nose 4. The means 30 is , for example, constituted by a helical spring, working at the compression, interposed inside the piston 25, between the latter and the compacting piston 8, to bear between the cap 22 and the end 31 of the metering piston 25 opposite the head 26. The metering piston 25 assumes an additional function of movable stop erasable relative to the compacting piston 8. To this end, the end 31 of the piston 25 is shaped to be placed on the straight path Alternative line of a shoulder 32 presented externally by the compacting piston 8 .

The movable stop function, assumed by piston 25, is accompanied by a possibility of adjustment in limited stroke of such a piston. This possibility is determined by a stop 33 with an adjustable position carried by the device to be placed on the straight stroke. Maximum possible alternative line of the metering piston 25. Such a stop 33 is, for example, constituted by a shim of adjustable thickness. or pre-determined, interchangeable, movable mounted while being carried by the base 1 to be engaging or retractable relative to the cylinder 6 in which the end 31 of the piston 25 slides. To this end, the adapter body 2 may have a Light 34. The _. device described above allows to implement

The following volumetric dosing process.

The supply of the chamber 24 maintains the piston 25 in the high position against the action of the opposing member 30 which is compressed. By means of the end 31, the piston 25 supports the compacting piston 8 by pressing on the shoulder 32. The opposing return member 21 is also maintained in a compressed state. In this position, the tubular rod or core 9 occupies a position of maximum withdrawal and delimits, with the end part of the rod 10, the metering chamber 11. It must be considered, although this is not shown, that means for adjusting the height of the chamber 11 could be interposed, in particular between the cap 22 and the head 26 of the piston 25.

By means of relative displacement, the device I is brought closer to the zone II so that the end open of the tubular rod 10 is brought close to, if not in contact with, the plane _P of this zone. It must be considered that the plan _P materializes the bottom of a reserve containing a charge of pulverulent product from which a volumetric dose must be taken.

During the previous phase, the means 18 are controlled to put the passage 16 and the cavity 7 under vacuum. By means of the rod or core 9 and the pellet 12, a suction effect is developed inside the chamber 11 which is thus caused to fill with pulverulent product during the downward movement of the device I .

After this operating phase, the stop 33 is introduced into the cylinder 6, providing for maintaining or interrupting the vacuum prevailing in the cavity 7. The pressurized fluid is extracted from the chamber 24, so that the piston 25 is stressed in downward movement under the action of the elastic member 30. The piston 25 therefore behaves like an abutment progressively disappearing in front of the shoulder 32 of the compacting piston 8 which follows the same movement while being stressed by the 'elastic member 21. The descent stroke of the two pistons continues until the end 31 meets the stop 33 which ensures its immobilization in a position as shown in fig.2.

During this descent, the rod or core 9 slides inside the cane 10 and ensures, by the pellet 12, a compaction of the dose of pulverulent product having filled the chamber 11 whose volume is gradually reduced. This compaction occurs between the pellet 12 and the plane P_ continuously under the effect of the constant pressure exerted by the opposing spring 21. Such a spring was calculated initially as a function of an average density of the pulverulent product, so that if the filling by suction-suction of the chamber 11 has intervened correctly, the mass of powdered product compacted in the chamber 11 then forms a compacted block 40 offering sufficient resistance to the action of the spring 21 to immobilize the piston of compaction 8, before the metering piston 25 is supported by its end 31 on the stop 33. In this way, the compaction piston is only subjected to the action of the spring 21 and transmits, via the rod or core 9, the restoring force of the latter, responsible for compacting the block 40. After this operating phase, a relative displacement is caused between the device I and the zone II to move the plane P_ away from the open end of the rod 10. During this movement, the compacting piston 8 slides, by the action of the spring 21, until it encounters, by the abutment shoulder 32, the end 31 of the piston 25 which constitutes a fixed abutment. During this movement, the rod 9 partially pushes the block 40 out of the chamber 11 whose residual height is thus limited to the adjustment of the stop 33 materialized, in the example illustrated, by the thickness of the shim constituting this stop. In fact, in this position, the compacting piston 8 is in positive abutment on the metering piston 25, which itself is immobilized positively by pressing against the stop 33 (FIG. 3).

After this operating phase, a scraping or leveling operation takes place with reference to the extreme transverse edge of the rod 10, so as to cut off the part 40aι of the compacted block 40 protruding from the chamber 11. The compacted block is thus limited to The part 40b always occupying the residual volume of the chamber 11 and corresponding to the desired volumetric dose. Due to the compacting undergone in the previous phase, the product ^pulverulent, constitutive of this dose, has a homogeneous density, regardless of its state in the reserve. It thus becomes possible, by such a method, to repeatedly produce volumetric doses whose volume-mass ratio differs only very slightly from each other, regardless of the overall or local density that the pulverulent product may have to be aspirated to constitute such a dose.

The distribution of the dose occurs, as illustrated in fig. 4, by ordering the extraction of the stop 33 for authorize the displacement of the metering piston 25 as far as the stop against the adaptation body 2. The compacting piston 8 follows the progressive recoil of the piston 25 and acts, by the rod 9, to expel, from the chamber 11, the part 40b of the compacted block 40, which represents the desired dose.

The expulsion phase can be completed by bringing the cavity 7 into contact with the circuit 17 then responsible for supplying a fluid under pressure.

The expulsion phase according to FIG. 4 can involve, prior to the extraction of the stop 33, a partial recharging of the chamber 25 in order to make the mobile assembly constituted by the piston 25 and the piston move back, partially 8.

Fig.5 shows schematically an installation for implementing the method of the invention by means of the device described above. Such an installation comprises, for example, a plate 50, preferably in horizontal orientation constituting the base 1 for one or, preferably, several devices I. Such a plate 50 can advantageously carry the stops 33 constituted by retractable wedges or by adjustable devices.

The plate 50 is arranged superimposed on a table 51, also horizontal, which is carried by a suitable frame or frame. Means, not shown, are provided for varying the relative vertical spacing between the plate and the table which may be, respectively, fixed and / or relatively mobile. These means are provided to allow complete release of the rod 10 relative to the reserve 52 and engagement of the rod until placing the free open end of the latter near the bottom P_ of the reserve.

The table 51 carries, plumb with the device or devices I, at least in a position for stopping the latter conferred by the plate 50, as many reserves 52 of powdered product to be sampled. These reserves can be constituted by bowls 53 mounted, by means of bearing 54, on the table 51, of so that they can rotate on their vertical axis x. The rotational drive can be provided permanently or cyclically by means of a motorization system 55.

The internal shape of the boL 53 can be variable and adapted to the specific nature of the pulverulent product to be dosed. The bottom of the bowl 53 represents the plane P_ described above. Each bowl 53 is associated with a recovery bucket 56 arranged laterally and having, in the upper part, a knife or a scraping or leveling blade 57 intended to cause, by relative displacement, the sectioning of the part 4θ of the compacted block 40 .

It is advantageously provided to have, between the core 9 and a stationary reference, such as the body 2, a position sensor, preferably adjustable. Such a sensor appreciates in this way the height of the chamber 11 after compaction. The detection of a height lower than that sought means that the suction filling phase has not taken place completely.

POSSIBILITY OF INDUSTRIAL APPLICATION:

The invention finds an interesting application in the production of cartridges with pyrotechnic effect.

Claims

CLAIMS:

1 - Method for volumetric dosing of pulverulent product with compaction, including the steps which consist of: a) - using an open tubular rod (10) provided internally with a core (9), b) - ordering the removal of the core (9) over a predetermined axial distance to delimit, inside the rod (10), a metering and compacting chamber (11), c) - engage in a reserve of product and up to proximity (P) from the bottom of this reserve the tubular rod (10) open, d) - suck, during c), by the core (9). sliding a dose of powdered product to fill the chamber (11), characterized in that it then consists of: e) - ordering a first partial advance of the core (9) to compact the dose against the bottom of the reserve and form a block (40) of compacted product in the chamber (11), f) - extract the rod ⁽ 10) from the reserve, g) - order a second partial advance of the core (9) to reduce the chamber (11 ) at the desired height and partially extend the block (40) from the open end of the rod (10), h) - level off the part (40_a_) of the protruding block outside the rod (10), i) - and controlling the total advance of the core (9) to eject the leveled block (40b) in a container responsible for receiving it.

2 - Method according to claim 1, characterized in that the suction is maintained by the core (9) during steps e) to f)

3 - Process according to claim 1, characterized in that the total advance of the core (9) is controlled and that at the same time a fluid pressure is delivered by the latter into the chamber. 4 - Process according to claim 1, characterized in that the height of the chamber is measured following the first partial advance of the core to assess the volume of the dose of product aspirated. 5 - Device for volumetric dosing of powdered product with compaction comprising:

- a tubular rod (10) open at its ends and extending an adapter body (2), said rod communicating with a circuit (17) for pressurization-depression, ~ a compacting piston (8) sliding relative to the cane including at its end a porous tablet (12) and capable of delimiting in the cane a metering chamber (11) with variable volume,

- means (20) for actuating the compacting piston during the straight stroke Alternate line set,

- And means (18) for cyclically controlling the operation of the pressurization-depression circuit, characterized in that:

the adapter body defines a cavity (7) which communicates with the pressure-depression circuit (17),

- The piston (8) is guided and sliding in the cavity (7) and is extended by a tubular rod (9) opening in the cavity (7), said rod being slidably engaged in the rod (10) for which it forms a core, carrying at its end the patch (12). 6 - Device according to claim 5, characterized in that the means (20) for actuating the compacting piston comprise at least one spring (21) responsible for driving said piston in the advance stroke of the core (9) inside the cane (10) and an opposing control means acting on this piston in the course of withdrawal of the core during which the latter delimits the metering chamber (11) inside the cane. 7 - Device according to claim 6, characterized in that the opposing means is constituted by a pneumatic cylinder with single effect.

8 - Device according to claim 6, characterized in that the means (20) for actuating the compacting piston (8) comprise a metering piston (25) slidably sliding on the compacting piston (8) for which it represents a stop mobile driven in erasure movement by a spring (30) on a stroke limited by a stop (33) with adjustable position, and in reverse return movement by a pneumatic cylinder (24).

9 - Device according to claim 8, characterized in that the metering piston (25) is slidably mounted around the compacting piston (8) and is guided both in a cylinder (6) formed in the adaptation body (2) coaxially with the cavity (7) and in a cylinder delimited (24) by a cap

(22) closing the body, one of said cylinders being connected to a circuit (29) of pressurized fluid.

10 - Device according to claim 8 or 9, characterized in that the metering piston (25) is limited in the erasure stroke relative to the compacting piston (8) by a stop (33) in the form of a retractable stop position adjustable insertable inside one of the cylinders.

11 - Device according to one of claims 8 to 10, characterized in that the metering piston (25) is associated with means for adjusting its reverse return stroke.

12 - Device according to claim 5, characterized in that the means for actuating the compacting piston (8) consist of a double-acting pneumatic cylinder.

13 - Installation for volumetric dosing of powdered product with compaction, characterized in that it comprises:

- at least one device according to one of claims 5 to 12 carried by a plate (50),

- a table (51) disposed under the tray and carrying at least one reserve (52) of powdered product associated with a scraper knife (57), 16

- And means for causing relative displacement, on the one hand, vertical and, on the other hand, horizontal between the tray and the table. 14 - Installation according to claim 13, characterized in that the means, for causing a vertical relative movement between the plate and the table, are designed to allow complete clearance of the rod (10) relative to the reserve (52) and an engagement of the rod until placing the open free end of the latter near the bottom (JP) of the reserve. 15 - Installation according to claim 13 or 14, characterized in that the reserve is constituted by a bowl (52) associated with means (55) for driving in rotation on its vertical axis.