EP2313259B1 - Device for forming tablets by constant volume compaction - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to the field of tablet design from component mixing, in the form of powders or granules in particular, and more particularly to a press device for forming such tablets by compaction.

STATE OF THE ART

The existing devices for making tablets by compaction are conventionally rotary presses provided with a rotating central plate in which is formed a plurality of through dies. On either side and facing each of the matrices are arranged lower and upper punches complementary to each other, and intended to be inserted into the corresponding matrix to compact the mixture it contains in order to form a compacted tablet at the desired volume. Indeed, the punches are provided with compaction ends whose surfaces define with the walls of the matrix a containment volume of the mixture, the punches being progressively closer to each other until reaching the compaction volume.

These devices operate in a cycle decomposing as follows: after a filling phase of the matrix with the mixture of compounds, the punches come closer to gradually constrain said mixture before an instantaneous final compaction where the punches impose a strong stress on the mixture of compounds. to form a tablet to the desired volume. Once the tablet is formed, it is ejected from the press. To achieve such a compaction cycle, it is known to use punches which are guided in a guide rail having a particular profile to control the axial displacement of the punches during the filling and ejection phase but also during the phase approximation of the punches before compaction itself. The actual compaction phase is carried out by compaction rollers on which the punches roll, and which allow to bring the punches instantaneously following a strong stress to form the tablet to the desired volume. A device according to the preamble of claim 1 is for example described in the patent application EP1600285 .

The applicant has however discovered that it may be interesting, in some applications, to keep the punches in a fixed compaction position so as to compress the mixture at a constant volume during an elongated compaction time. Useful reference will be made to the French patent application filed on July 18, 2008 under the number FR0854909 , for a more complete description of the constant volume compaction cycle, and the corresponding applications.

The applicant has therefore sought to develop a rotary press for performing such compaction at constant volume. To do this it is necessary to keep the punches at a fixed compaction position so that the confinement volume (defined by the matrix and the lower and upper punches) is kept constant. One solution is to use a particular compaction member composed of compacting rollers and ball bearings arranged to maintain the punches at a fixed axial position, and to lengthen the compaction. Such a solution is however complex to implement, and it is not very precise since the axial position of the punches varies significantly with respect to the set position, as a function of the contact surface with the roller / bearing. In addition, such a solution is not easily adaptable, particularly as regards the holding time punches.

An object of the present invention is therefore to provide a press adapted to maintain a compaction at a constant volume for a predetermined time to solve at least one of the aforementioned drawbacks.

In particular, an object of the present invention is to provide a press for maintaining a constant volume compaction easily adaptable to any type of product, rate, and holding time.

Yet another object of the present invention is to provide a press for maintaining a constant volume compaction that can be used at industrial rates, for increased productivity, and whatever the type of product to compact.

SUMMARY OF THE INVENTION

For this purpose, there is provided a press device for making tablets from a mixture of at least one component according to claim 1.

The fact of using a planar cam portion having an angular section of between 5 ° and 170 ° is particularly advantageous since it makes it possible to compact mixtures during compaction holding times of between 100 and 2500 ms, and this in a wide range. range of rotational speed of the press to ensure a good industrial rate. The fact of being able to compact at various speeds of rotation makes it possible to compact any type of mixture during the compaction times indicated (between 100 and 2500 ms), including the mixtures requiring a reduced rotation speed of the press (of the order a dozen revolutions per minute).

In addition, the productivity is even better than such an angular section for the flat cam portion also allows to have a press comprising at least two outputs.

The fact that the planar cam portion has a length furthermore implies that several punches are simultaneously on the cam path, which makes it possible to further increase the rate of formation of tablets according to a compaction cycle having a step of maintaining compaction. Indeed, if several punches are simultaneously on the flat cam portion, this implies that several tablets can be compacted simultaneously on the same flat cam portion with only a slight shift in the compaction cycle.

• la portion plane du chemin de came s'étend sur une section angulaire comprise entre 35° et 90° ;
• le chemin de came de la came de compaction comprend en outre une portion de montée en pression située en amont de la portion plane de maintien en compaction, la portion de montée en pression étant adaptée pour déplacer axialement le premier poinçon dans le sens d'une insertion du premier poinçon dans la matrice, vers la position axiale de maintien en compaction ;
• le chemin de came de la came de compaction comprend en outre une portion de descente en pression située en aval de la portion plane de maintien en compaction, la portion de descente en pression étant adaptée pour déplacer axialement le premier poinçon dans le sens d'un retrait du premier poinçon de la matrice, à partir de la position axiale de maintien en compaction ;
• l'organe de guidage comprend deux galets agencés de part et d'autre du premier poinçon de manière à pouvoir rouler dans des gorges agencées de part et d'autre de la trajectoire circulaire définie par le déplacement de la matrice ;
• la came de compaction comprend au moins un capteur de contrainte disposé dans une cavité ménagée dans la came pour mesurer les contraintes subies par le chemin de came au passage du premier poinçon ;
• la came de compaction comprend trois capteurs de contrainte répartis dans trois cavités ménagées dans la came, lesdites trois cavités étant respectivement formées au centre et aux deux extrémités de la portion plane du chemin de came ;
• les deuxièmes moyens de commande ont une configuration identique aux premiers moyens de commande ;
• le deuxième poinçon a une configuration identique au premier poinçon ;
• le premier poinçon et le deuxième poinçon correspondent respectivement au poinçon inférieur et au poinçon supérieur de la presse, les premiers et deuxièmes moyens de commande correspondant aux moyens de commande inférieurs et supérieurs respectivement.

Preferred but non-limiting aspects of the above press device are:

• the flat portion of the cam path extends over an angular section of between 35 ° and 90 °;
• the cam path of the compaction cam further comprises a pressure increase portion located upstream of the planar holding portion in compaction, the pressure increase portion being adapted to axially move the first punch in the direction of a insertion of the first punch in the matrix, towards the axial position of maintaining in compaction;
• the cam path of the compaction cam further comprises a pressure descent portion located downstream of the planar holding portion in compaction, the pressure descent portion being adapted to axially move the first punch in the direction of a removing the first punch from the matrix, from the axial position of maintaining compaction;
• the guide member comprises two rollers arranged on either side of the first punch so as to be able to roll in grooves arranged on either side of the circular path defined by the displacement of the die;
• the compaction cam comprises at least one strain sensor disposed in a cavity formed in the cam for measuring the stresses experienced by the cam path at the passage of the first punch;
• the compaction cam comprises three stress sensors distributed in three cavities formed in the cam, said three cavities being respectively formed at the center and at the two ends of the flat portion of the cam path;
• the second control means have a configuration identical to the first control means;
• the second punch has a configuration identical to the first punch;
• the first punch and the second punch respectively correspond to the lower punch and the upper punch of the press, the first and second control means corresponding to the lower and upper control means respectively.

DESCRIPTION OF THE FIGURES

• La figure 1 est une représentation tridimensionnelle en coupe d'un dispositif de presse rotative ;
• La figure 2 est un schéma illustrant l'entrainement en rotation des poinçons dans le dispositif de presse rotative ;
• la figure 3 est une représentation tridimensionnelle en éclaté du dispositif de presse selon l'invention ;
• la figure 4 est une représentation en vue de dessus d'une came de compaction utilisée pour le dispositif de presse ;
• la figure 5 est une représentation schématique mettant en avant le positionnement des poinçons sur les cames de compaction associées pendant la phase de compaction avec un dispositif de presse selon l'invention ;
• la figure 6 est une représentation tridimensionnelle d'un poinçon avec galet de roulement selon un mode particulier de réalisation de l'invention ;
• la figure 7 est une représentation tridimensionnelle d'un poinçon avec galet de roulement selon un autre mode de réalisation de l'invention.

Other features and advantages of the invention will become apparent from the description which follows, which is purely illustrative and nonlimiting and should be read with reference to the accompanying drawings, in which:

• The figure 1 is a three-dimensional representation in section of a rotary press device;
• The figure 2 is a diagram illustrating the rotational drive punches in the rotary press device;
• the figure 3 is an exploded three-dimensional representation of the press device according to the invention;
• the figure 4 is a top view of a compaction cam used for the press device;
• the figure 5 is a schematic representation highlighting the positioning of the punches on the compaction cams associated during the compaction phase with a press device according to the invention;
• the figure 6 is a three-dimensional representation of a punch with a roller according to a particular embodiment of the invention;
• the figure 7 is a three-dimensional representation of a punch with a roller according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The figure 1 is a perspective sectional view of a rotary press device which makes it possible to illustrate the structure conventionally used to drive the compaction punches according to a rotary movement.

The rotary press device comprises a turret which is rotated by a known motorization system via a central drive axis. The turret comprises a central plate 1 which comprises at least one compaction matrix 2, this matrix 2 being intended to receive a mixture of compounds from which it is desired to form a compacted tablet at a determined volume.

The central plate preferably comprises a plurality of matrices 2 distributed for example at the periphery of the central plate 1 which has a substantially circular shape. Said matrices 2 have a generally cylindrical shape and are either formed by a through hole directly formed at the periphery of the central plate 1, or each die is a specific part comprising a cylindrical through central opening having a circular section with a determined diameter corresponding to the desired diameter for the tablet, this piece serving as a matrix having an external shape adapted to be inserted into through openings formed at the periphery of the central plate 1.

As indicated above, the press device comprises punches (not shown on the figure 1 ) which are arranged on either side of each of the dies 2 of the central plate 1. Preferably, the device comprises a lower pair of punches 3 and upper 4 for each of the matrices 2 of the device. The lower and upper punches 4 are mounted in the press so as to be axially displaceable with respect to the corresponding die 2, so that said lower and upper punches 4 can be inserted into the die 2 to compress the mixture disposed at the inside of the matrix to form a tablet at a determined volume.

The lower 3 and upper 4 punches are also mounted in the press so as to have a circular movement corresponding to the circular movement of the matrix 2 with which they are associated. A solution for setting the punches in motion along this circular path is to use training plates 5 and 6 located on either side of the central plate 1, these two training plates 5 and 6 being integral with the central plate. 1 and thus being also rotatably mounted in the press. The drive plates 5 and 6 are provided with through openings disposed at their periphery, these through openings being intended to receive the lower punches 3 and upper 4 respectively. The lower and upper punches 4 are thus rotated by the drive plates 5 and 6, respectively, synchronously with the corresponding die 2, the lower and upper punches 4 being moreover able to slide in the openings provided at the periphery. drive trays 5 and 6 so that the compaction ends 31 and 41 of the lower and upper punches 3 and 4 can be inserted into the die 2.

The axial displacement of the lower 3 and upper 4 punches is controlled by lower control means 7 and upper control means 8 respectively, these lower 7 and upper 8 control means being intended to cooperate with the guide ends 32 and 42 of the punches lower 3 and upper 4 respectively. The control means are intended to move the corresponding punches along the axis of the die so as to modify the axial position of the punch (and more particularly the axial position of the compaction end of the punch) according to the operating cycle of the press. The axial position of a punch is defined as the position of the punch in the axis of the die, this position thus making it possible to characterize the axial displacement of the punch, but also the associated confinement volume.

Among the different phases of the operating cycle of the press, there is a compaction phase during which the lower 3 and upper 4 punches are moved so as to be inserted in the corresponding matrix 2 to reduce the confinement volume, until to reach a volume of compaction that one seeks to maintain constant for a certain time.

The lower control means 7 and upper 8 are adapted to cooperate so as to maintain, for a predetermined time, the lower 3 and upper 4 punches in an axial fixed compaction position in which these lower 3 and upper 4 punches define with the matrix 2 associated a fixed confinement volume corresponding to the compaction volume adapted to form a tablet with a certain volume. To do this, the compaction volume is substantially equal to the final volume sought for the tablet. Preferably, the compaction volume corresponds to the final volume sought for the tablet. It may, however, in certain cases be possible for the compaction volume to be slightly less than the final volume desired for the tablet; this is for example the case when tablet compressed compounds still have a certain elasticity.

To do this, one of the two control means comprises a particular compaction cam. In the following description, it is considered that the lower control means 7 for moving the lower punches 3 comprise said particular compaction cam. This description is however not limiting since a compaction cam as described below could also be used for the upper control means 8, or both for the lower control means 7 and upper 8.

The compaction cam 9 comprises a cam path on which the corresponding punches are able to move, this cam path having a trajectory corresponding at least partially to the circular trajectory defined by the movement of the matrices 2.

Said compaction cam 9 comprises a flat portion 90 substantially perpendicular to the axis of the punch 3 which moves on the cam. Thus, a punch that moves on this flat cam portion 90 has a fixed axial position maintained for a predetermined time. Indeed, the flat portion 90 extends over an angular section which is adapted to maintain the punch inserted in the die 2 at the desired fixed position, to maintain a constant compaction volume during a holding time. determined. The angular section of the planar cam portion is defined as the angle formed by the planar cam portion relative to the center of the circular path of the punches. The length of the flat cam portion is further defined as the distance traveled by the punch on said flat cam portion when the punch is rotated by the associated drive plate.

The dimensioning of the flat cam portion 90, particularly with regard to its angular section, depends on the time during which it is desired to maintain the compaction volume constant, and the rotational speed at which the punches are driven in the press. As mentioned later, the hold time of the constant volume compaction of conventional systems is less than 30 ms (milliseconds). The rotational speeds for a rotary press used in production are between 18 and 30 revolutions / minute, which corresponds to flat cam portions with an angular section of 3.24 ° and 5.4 ° respectively, for a time compaction hold at constant volume of 30 ms. If a press with a lower rotational speed is used, the angular section of the planar cam portion necessary for 30 ms constant volume compaction is reduced; it is for example 0.36 ° for a rotation speed of 2 revolutions / minute. The angular section of the planar cam portion will be larger the longer it is desired to maintain constant volume compaction (for a given rotational speed of the press). The compaction cam 9, and in particular the flat cam portion 90, is adapted as a function of the time during which it is desired to maintain the compaction at constant volume, but also as a function of the operating parameters of the press (rotation speed, diameter , etc.). The use of the planar cam portion to maintain a constant compaction volume is all the more advantageous as it is very simple to adapt and / or set up a new cam in the press. In addition, the rotational speed of the press can also be modified to achieve the desired holding time for a flat cam portion having a given length (and thus a given angular section).

The upper control means 8 are also adapted to maintain the upper punch 4 in a fixed axial position while the lower punch 3 is held in fixed axial position by cooperation with the flat cam portion 90. To do this, the control means upper members 8 comprise a compaction cam 10 having a flat cam portion 100 extending over an angular section at least equal to the angular section of the cam portion 90 of the compaction cam 9. However, in an example not making part of the invention any other means for maintaining fixed axial position of the upper punch 4 may be considered. It could for example be used a system of upper punches 4 whose axial displacement is prohibited, the upper punches 4 being then held in the matrix 2 at a defined fixed axial position. It could also be envisaged to have a press device with only lower punches 3 intended to be inserted in non-through matrices 2, that is to say having a "blind hole" type opening.

The fact that the lower punch 3 moves on the flat cam portion 90 for a predetermined time (defined both by the angular section over which the flat cam portion 90 extends, and by the speed of rotation of the punches) implies that the compaction end 31 of the lower punch 3 is held in the die 2 at a fixed axial position for a predetermined time, the compaction end 41 of the upper punch 4 also being held in the die 2 at a fixed axial position , so that the lower punch 3, the upper punch 4 and the die 2 form a confinement volume held fixed for the same determined time, this confinement volume corresponding to the compaction volume adapted to form the tablet. In a preferred manner, the different elements of the press device are adjusted so that the lower and upper punches 4 define with the matrix 2, during this compaction holding time, a fixed compaction volume corresponding to the final volume of the Tablet.

The guide end 32 of the lower punch 3 is formed so that said lower punch 3 can move on the compaction cam 9 so as to be able to respond to compaction constraints to form the desired tablet. In particular, the punches must be able to withstand the forces induced by the compaction of the mixture, and the friction forces are reduced to a minimum. The sum of the forces induced by the punches during compaction, generates a significant torque in the training of the turret. The use of standard punches requires the mounting of a motor with a much larger torque and therefore a dimension, intensities, powers much larger. The friction generated by the set of punches emit, when standard, a significant heat energy and a rapid degradation of the cams.

Thus, it is proposed to use a guide end 32 comprising a roller 33 arranged so that the lower punch 3 can roll on the cam path of the compaction cam 9 along the partially circular path defined. The rolling roller 33 is arranged coaxially with the axis of the lower punch 3 at its guide end 32, with an axis of rotation that is radial relative to the axis of the punch. The use of such a rolling roller 33 makes it possible to considerably reduce the friction caused by the displacement of the lower punch 3 on the compaction cam 9, which is particularly advantageous for maintaining compaction stresses large, typically greater than 1 KN (kilo-Newton), for prolonged holding times in compaction compared to conventional rotary press systems. Indeed, it is sought to maintain a constant compaction volume for a relatively long time of between 100 ms to 2500 ms compared to conventional systems that perform compactions that can be described as instantaneous (of the order of a few milliseconds, typically less than 30 ms).

The rolling roller 33 is sized according to the stress constraints to which the press device is subjected. It can therefore be adapted according to the composition of the mixture to be compacted. The dimensioning of the rollers must make it possible to accept the axial forces without degrading the cam surface on which they roll (lifespan compatible with the maintenance aspects) while allowing a mounting of punches in sufficient number to maintain a good productivity per revolution. turret. Thus, it is possible, for example, to use rollers of greater or lesser diameter, depending on the stresses to which the press device is subjected for the compaction of a particular mixture. When the stress of effort is important, a solution for not having a diameter too large for the roller, which is not necessarily compatible with the size of the press, is to use for a punch two rollers rolling (33a, 33b) side by side. Such a solution makes it possible to use rollers with smaller diameters for the same stress of effort, which is therefore particularly advantageous in terms of compactness of the press. For example, it is possible to use two rollers (33a, 33b) placed side by side with a diameter of 62 mm, in place of a single rolling roller with a diameter of 110 mm.

Both solutions, with single roller and double rollers, are illustrated in the drawings. Figures 6 and 7 respectively.

In addition to the flat portion 90 corresponding to the compaction holding phase of the compaction phase, the compaction cam 9 may further comprise a pressure increase portion 91 and a pressure descent portion (not shown).

If we consider the direction of rotation of the punches, the pressure increase portion 91 is situated upstream of the planar holding portion 90, this pressure increase portion 91 being adapted to move the lower punch 3 into the direction of insertion in the matrix 2 until the axial position corresponding to the fixed axial position of compaction holding defined by the plane portion 90 compaction maintaining.

The pressure rise portion 91 makes it possible to progressively move the lower punch in the die 2, and it is adapted to prepare the mixture for the final compaction. The compaction cam 9 may also comprise a pressure descent portion situated downstream of the planar holding portion 90, again with reference to the direction of rotation of the punches in the press device. This pressure descent portion 92 serves to reduce the compaction volume defined by the lower punch 3, the upper punch 4 and the die 2. Thus, this pressure descent portion is preferably arranged so as to move the punch axially. lower 3 as well as the upper punch 4 for extraction of the upper compaction end 4 of the matrix 2.

This pressure descent portion is however not necessary since the reduction of the confinement volume (defined by the lower punch 3, the upper punch 4 and the matrix 2) can be effected by an axial displacement of the upper punch 4 in order to From a particular embodiment, the planar portion 90 of compaction of the compaction cam 9 can even be followed by a cam portion 11 arranged to axially move the lower punch 3 to increase. its insertion into the die 2. Such a cam portion 11 may be called an extraction cam, arranged to expel out of the die 2 the tablet formed during the compaction phase by the compaction-holding cam 90, in such a way that to recover this tablet and to be able to refill the matrix 2 with the mixture of compounds before reforming a new tablet.

As we have just seen, the lower control means 7 further comprise the compaction cam 9 which makes it possible to manage the axial displacement of the lower punch 3 during the compaction phase strictly speaking, guiding means enabling the punch to be moved axially. lower 3 during other phases of the cycle of operation of the press. The extraction cam 11 is a particular example of such additional guide means, this extraction cam 11 being used to push the tablet out of the die 2 during the extraction phase following the compaction phase.

The lower control means may also include a metering cam with a particular cam path for moving the lower punch 3 adequately during filling of the die 2 with the compound mixture. It is arranged upstream of the compaction cam 9, preferably immediately before said compaction cam 9.

The lower control means 7 may also comprise other guide members allowing, for example, the lower punch 3 to be displaced between the different important phases of the operating cycle of the press, in order to put the punches in position. To this end, it will be possible for example to use one or more guide rails 12 arranged along the circular path defined by the displacement of the dies 2, these rails being provided to cooperate with a guide member 34 provided at the guide end. 32 of the lower punch 3. The lower punch 3 may for example be provided with guide rollers 34 arranged coaxially with the axis of said punch with an axis of rotation radial relative to this punch, the two guide rollers 34 being located from and other punch. In this case, the guide rails 12 are provided with a groove in which the guide rollers 34 can roll. It is the cooperation of these guide rollers 34 in the grooves which makes it possible to axially move the lower punch 3.

The figure 4 illustrates an example of a cam for the punch control means. The cam shown in plan view comprises a first cam portion 13 (in the direction of rotation of the punches) corresponding to the metering cam, this metering cam 13 being followed by a pressure increase cam portion 91, then of the pressure maintaining cam portion 90. The arrow represented on this figure 4 illustrates the direction of movement of the punches on the cam.

The figure 5 illustrates a device in which the lower control means 7 comprise cams with cam portions similar to the cam shown in FIG. figure 4 that is, a metering cam portion 13, a pressure rise cam portion (91), and a compaction holding cam portion (90). The upper control means also includes a planar cam portion (100) for holding the punch in position during compaction, which planar cam is also preceded by a pressure rise cam (101). The arrow represented on this figure 5 illustrates the direction of movement of the punches on the cams.

The figure 5 illustrates a particular embodiment of the press device shown wherein the lower control means 7 and upper 8 both comprise a planar portion for maintaining compaction, and a pressure increase portion. It should be noted that in this particular case, the upper punches 4 have a structure similar to the lower punches, and they include in particular preferably at least one roller (43), or even guide rollers (44). In addition, the upper control means 8 are in this particular case provided with means adapted to retain the upper punches 4 against the effect of gravity.

The figure 5 also makes it possible to illustrate the movement of the lower and upper punches 4 inside the matrix 2 during their displacement on the cams of the lower and upper control means 7 and 8. It can thus be seen that the volume (V) is progressively reduced when the punches roll on the pressure increase cams (91; 101) while the same containment volume (V) remains fixed (at a compaction volume substantially corresponding to the final volume of the tablet) when the punches roll on the compaction maintaining cams (90; 100).

According to a preferred embodiment, at least one of the compaction cams comprises sensors making it possible to follow the compaction stress defined by the action of the lower 3 and upper 4 punches on the mixture of compounds to be compressed. It is also possible to provide distance sensors for monitoring the axial position of the lower and / or upper punches 4.

For example, it is possible to provide one or more cavities in the flat cam portion to insert stress sensors for measuring the stresses to the cam path when the punch passes. This stress can then be directly related to the compaction stress imposed on the mixture of compounds.

On the Figures 4 and 5 is illustrated a possible positioning of three sensors (C1; C2; C3) of stresses in the compaction cams. In this particular example, they are arranged at the beginning and at the end of the compaction holding phase and in the middle of this phase. The more sensors arranged in the compaction cam, the more precise the tracking of the constant volume compaction will be.

The use of these stress sensors, in particular the stress sensors placed in the camming portion 90 of compaction, are particularly advantageous for monitoring the behavior of the mixture of compounds when it is compacted at a constant volume for a predetermined time. . As mentioned below, these stress sensors can in particular be used to determine and / or adjust the compaction cycle to be applied to the mixture to be compacted. The sensor measures the effort of a single punch and the passage of each punch; unlike a stress sensor associated with a compression roller which measures the sum of the forces of the punches in contact with this roller.

In addition, these strain sensors can be used to control the proper operation of the press and punches. In particular, the stress sensors can be used to prevent any disturbance of the press, particularly as regards the positioning of the cam paths (parallelism, relative difference, etc.), and / or by controlling the compaction at strategic points. of the compaction cycle.

It will be noted that the use of stress sensors is independent of the length chosen for the camming portion 90 of compaction, so that it is conceivable to have such sensors regardless of the angular section of the cam portion. 90 of keeping in compaction.

As indicated above, the applicant has discovered that it may be advantageous to form tablets from certain compounds by keeping them at a constant compaction volume for a given time, long enough for the compacted mixture to undergo particular physical transformation that will significantly improve the properties of the tablet, especially in terms of strength. For more detail on the particular method of compaction that can be implemented by the press according to the invention, reference will be made to the French patent application filed July 18, 2008 under the number FR0854909 .

In particular, it is possible to use the press of the invention for the compaction of pulverulent compositions comprising at least one powder having elastic properties or hot-melt properties, but also to the compaction of pulverulent compositions having a tendency to change state during compaction. for example passing from a solid state to a pasty or liquid state. They may be pulverulent compositions having a high moisture content. By "elastic" is meant a material that has the property to take back, partially or totally, its shape or its volume, after having lost by compression or extension. By "hot melt" is meant a material that becomes fluid under the effect of heat.

In one embodiment, the press is used to compact powder compositions consisting of a powder or a mixture of powders, at least one of which has elastic or hot-melt properties.

In a particular embodiment, the press is used for the compaction of pulverulent compositions based on plant materials. The compaction can be implemented with plant ingredients such as coffee, tea or chicory or plant ingredients suitable for making herbal teas such as thyme, rosemary, linden, ginseng, ginko, marjoram, mint, verbena, ginger, wild yam, plants of the rosmarinus officinalis family, and mixtures thereof. The plant compounds used in the invention are generally in the form of grains or broken or crushed leaves, and having optionally undergone one or more prior treatment known per se. The process according to the present invention can in particular be applied to materials such as cellulose, hemicellulose, lignin or any mixture of the above compounds. The invention can also be applied to wood fibers, algae, tea, aromatic herbs, stems of dry crushed plants, compost, dried flowers. (to be completed by other plant materials)

In another embodiment of the invention, the press is used for the compaction of laundry washing compositions. These compositions typically comprise: sequestering agents, alkaline agents, bleaching agents, surfactants (in liquid, solid form, supported on zeolites, bentonites or clays in general) anionic, cationic or nonionic, activators of the bleaching agent, enzymes, splitting agents, perfume binders, dyes, defoamers, optical brighteners, anti-blocking agents color transfer (to be completed by main ingredients) of which (to be supplemented by elastic ingredients) cellulose-type bursting agents have elastic properties, binding agents eg solid polyethylene glycol, solid surfactants type SDS, or supported liquid surfactants on bentonite have hot melt behaviors.

According to yet another embodiment of the invention, the press shown is used for the compaction of compositions for washing dishes.

The presented press makes it possible to progressively compact an initial volume of powder until a desired volume of compaction is reached at which the powder is maintained for a given time. This makes it possible to obtain a solid compact product from a powdery composition.

Once the mixture has been inserted into the matrix, the punches are moved by the compaction cam 9 to progressively compact the pulverulent composition to the compaction volume that it is desired to maintain constant. The compaction volume is smaller than the initial volume of the uncompacted powder composition. Moreover, the compaction volume is less than or equal to the determined or final volume of the compacted product. Indeed, as has already been said, when the powdery composition is particularly elastic, there may be a slight extension of the product during release of the volume constraint. In an advantageous embodiment, the compaction volume is between 20 and 90% of the initial volume of the pulverulent composition, and preferably between 30 and 75% of the initial volume.

The particular structure of the press makes it possible to maintain the pulverulent composition at a constant volume which corresponds to the compaction volume for a given time. The time at which a constant compaction volume is maintained is chosen according to the characteristics required for the final compacted tablet. The hold time can be determined experimentally.

When the compaction volume is kept constant, the press, and more precisely the punches and the associated compaction cams, are subjected to stress stresses due to the strength of the pulverulent composition. During the compaction step at constant volume, the resistance of the powdery composition gradually decreases, stress constraints on the press thus decreasing concomitantly.

The measurement of these stress stresses during constant volume compaction makes it possible to determine the compression curve of a given pulverulent composition and to deduce the minimum time during which the composition must be maintained at the constant compaction volume. This measurement can be done on a laboratory press. The press according to the invention can also be used to make this particular measurement, provided that there are enough stress sensors arranged in the pressure holding cams. In practice, it will be possible to use three strain sensors placed in the camming portion 90 of compaction, respectively at the beginning, in the center, and at the end of the camming portion 90 of compaction, that is, say at both ends and in the center of the camming portion 90 of compaction. It is also possible to use the press according to the invention to confirm the results of the laboratory, and / or to verify that the behavior of the compacted mixture is similar under industrial conditions.

Once the minimum time for maintenance at constant volume is determined, it is necessary to adjust the press so that it is adapted to these compaction conditions, or even to size the compaction cam 9 (more precisely the plane holding portion in compaction 90) and / or the rollers of the punches.

Below are examples illustrating the determination of the holding time in compression, and the sizing of the corresponding press, for different compositions to be compacted.

Example 1

Roasted and milled coffee of average size 1 mm, with a loss of 4% volatile matter after a stay of 20 minutes at 120 ° C, is compacted using a compaction system to arrive at a constant controlled volume. The punch used for this compression is a round punch of diameter 32 mm with chamfer. 7 grams of this product are introduced into the containment chamber representing a filling height of 27.3 mm. The final compression height is set at 8.3 mm leading to a volume reduction of 70%. This compression height is maintained for a time of 850 milliseconds. The maximum effort measured is 40KN, and only 20 KN after 850 milliseconds of hold time. We can therefore deduce that it is necessary to ensure a holding time in order to obtain a cohesive tablet. In this case the minimum hold time to obtain a cohesive and transportable tablet is 850 milliseconds. At 850 milliseconds the resulting force is 20 KN. The fall of this holding force is equal to 50%.

The press is dimensioned and / or adjusted so that it can maintain a compaction volume for a time of at least 850 milliseconds, and withstand forces of the order of 40 KN. To do this, a compression cam having an angular section of at least 56.1 °, for a press having a rotational speed of 11 rpm. In addition, the punches preferably have a roller having a diameter of 62 mm, and a width of 56 mm.

Example 2

Ground roasted and ground coffee of average size 1 mm, with a loss of volatile matter of 3.3% after a residence time of 20 minutes at 120 ° C, is compacted by means of a compaction system allowing to arrive at a constant controlled volume. The punch used for this compression is a round punch of diameter 32 mm with chamfer. 7 grams of this product are introduced into the containment chamber representing a filling height of 27.3 mm. The final compression height is set at 8.3 mm leading to a volume reduction of 70%. This compression height is maintained for 800 milliseconds. The maximum effort measured is 40 KN, and only 20 KN after 800 milliseconds of hold time. We can therefore deduce that it is necessary to ensure a holding time in order to obtain a cohesive tablet. In this case the minimum hold time for a cohesive and transportable tablet is 400 milliseconds. At 400 milliseconds the resultant force is 30 KN. The fall of this holding force is equal to 25%.

The press is dimensioned and / or adjusted so that it can maintain a compaction volume for a time of at least 400 milliseconds, and withstand forces of the order of 40 KN. To do this, a compression cam having an angular section of at least 43.2 ° is used for a press having a rotation speed of 18 rpm. In addition, the punches preferably have a roller having a diameter of 62 mm, and a width of 56 mm.

Example 3

A Eurotab® linen formulation called 30458 is tested in order to check whether it is necessary to maintain a constant volume maintenance time to obtain a cohesive and transportable tablet. The composition to be compacted is indicated in Table 1 below: <i> Table 1 - composition of laundry formulation 30458 (Eurotab company </ i> ® <i>) </ i> COMPOUNDS % by weight Sequestering agents (phosphates, citrate, polymers, zeolite ...) 35-50% Alkaline agents (sodium silicate, carbonate) 10-30% Charge (bicarbonate, sodium sulfate ...) 3-20% Nonionic and anionic surfactants 10-18% enzymes 0.5-3% Bleaching agents and activator 10-20% Binder (polyethylene glycol powder ...) 1-5% Disintegrating agents (cellulose ...) 2-8% Optical brightener 0-1% Anti foam 0-1% perfume 0.5% - 1% dye 0.05% -0.1%

For this test a round punch 45 mm in diameter with chamfer, standard punch for tablet application, is used. 40 grams of this formulation 30458 are introduced into the compaction chamber representing a filling height of 38 mm. The final compression height is set at 18 mm, resulting in a volume reduction of 53%. This compression height is maintained for 800 milliseconds. The maximum effort measured is 31.5 KN, and only 18 KN after 800 milliseconds of hold time. We can therefore deduce that it is necessary to ensure a holding time in order to obtain a cohesive tablet. In this case the minimum hold time to obtain a cohesive and transportable tablet is 100 milliseconds. At 112 milliseconds the resultant force is 28KN. The fall of this holding force is equal to 11%.

The press is dimensioned and / or adjusted so that it can maintain a compaction volume for a time of at least 100 milliseconds, and withstand stresses of the order of 32 KN. To do this, a compression cam having an angular section of at least 10.8 ° is used for a press having a rotation speed of 18 rpm. In addition, the punches preferably have a roller having a diameter of 62 mm, and a width of 56 mm.

Example 4

ARBOCEL ™ TF415 (cellulose), marketed by Rettenmaier®, is tested in order to check whether it is necessary to maintain a constant volume hold time to obtain a cohesive and transportable tablet. For this test a round punch of diameter 32 mm with chamfer is used. 8.45 grams of this ARBOCEL ™ TF415 are introduced into the compaction chamber representing a filling height of 28 mm. The final compression height is fixed at 9 mm, resulting in a volume reduction of 68%. This compression height is maintained for 800 milliseconds. The maximum effort measured is 21 KN, and only 8 KN after 800 milliseconds of hold time. We can therefore deduce that it is necessary to ensure a holding time in order to obtain a cohesive tablet. In this case the minimum hold time to obtain a cohesive and transportable tablet is 300 milliseconds. At 300 milliseconds the resulting force is 18 KN. The fall of this holding force is equal to 14.3%.

The press is dimensioned and / or adjusted so that it can maintain a compaction volume for a time of at least 300 milliseconds, and withstand stresses of the order of 21 KN. To do this, a compression cam having an angular section of at least 19.8 ° is used for a press having a rotation speed of 11 rpm. In addition, the punches preferably have a roller having a diameter of 62 mm, and a width of 56 mm.

The fact of using a planar cam to maintain compaction is particularly advantageous so that the press has high production rates. Indeed, the use of the planar compacting cam keeps compaction for a relatively long time, for example of the order of 800 ms or even 2500 ms, without the rate of formation of tablets. by the press is reduced. Indeed, the use of holding cams implies that several punches are simultaneously on the cam path, and therefore that several tablets can be compacted simultaneously on the same flat cam portion, with only a slight shift in the compaction cycle.

Table 2 below illustrates the minimum angular sections of the flat cam portion, for different holding times of the constant volume compaction, and for different rotational speeds of the press. These values are of course not limiting and the section of the flat cam portion will be adapted as a function of the desired time to maintain the compaction at a constant volume; the angular section of the flat cam portion can therefore be between these values or be larger, for a given rotation speed. The reasoning is the same if the speed of rotation of the press is changed. <i> Table 2 - Examples of angular sections for the flat cam portion for different holding times and different rotational speeds of the press </ i> Speed of rotation of the press (in revolutions / minute) Angular section of the flat cam portion (in degrees) versus the compaction hold time (in ms) 30 ms 100 ms 300 ms 400 ms 750 ms 800 ms 850 ms 1000 ms 1500 ms 2000 ms 2500 ms 3000 ms 2 0.4 ° 1.2 ° 3.6 ° 4.8 ° 9.0 ° 9.6 ° 10.2 ° 12.0 ° 18.0 ° 24.0 ° 30.0 ° 36.0 ° 5 0.9 ° 3.0 ° 9.0 ° 12.0 ° 22.5 ° 24.0 ° 25.5 ° 30.0 ° 45.0 ° 60.0 ° 75.0 ° 90.0 ° 8 1.4 ° 4.8 ° 14.4 ° 19.2 ° 36.0 ° 38.4 ° 40.8 ° 48.0 ° 72.0 ° 96.0 ° 120.0 ° 144.0 ° 10 1.8 ° 6.0 ° 18.0 ° 24.0 ° 45.0 ° 48.0 ° 51.0 ° 60.0 ° 90.0 ° 120.0 ° 150.0 ° 180.0 ° 11 2.0 ° 6.6 ° 19.8 ° 26.4 ° 49.5 ° 52.8 ° 56.1 ° 66.0 ° 99.0 ° 132.0 ° 165.0 ° 198.0 ° 15 2.7 ° 9.0 ° 27.0 ° 36.0 ° 67.5 ° 72.0 ° 76.5 ° 90.0 ° 135.0 ° 180.0 ° 225.0 ° 270.0 ° 18 3.2 ° 10.8 ° 32.4 ° 43.2 ° 81.0 ° 86.4 ° 91.8 ° 108.0 ° 162.0 ° 216.0 ° 270.0 ° 324.0 ° 20 3.6 ° 12.0 ° 36.0 ° 48.0 ° 90.0 ° 96.0 ° 102.0 ° 120.0 ° 180.0 ° 240.0 ° 300.0 ° 360.0 ° 25 4.5 ° 15.0 ° 45.0 ° 60.0 ° 112.5 ° 120.0 ° 127.5 ° 150.0 ° 225.0 ° 300.0 ° - - 30 5.4 ° 18.0 ° 54.0 ° 72.0 ° 135.0 ° 144.0 ° 153.0 ° 180.0 ° 270.0 ° 360.0 ° - - 35 6.3 ° 21.0 ° 63.0 ° 84.0 ° 157.5 ° 168.0 ° 178.5 ° 210.0 ° 315.0 ° - - - 40 7.2 ° 24.0 ° 72.0 ° 96.0 ° 180.0 ° 192.0 ° 204.0 ° 240.0 ° 360.0 ° - - - 45 8.1 ° 27.0 ° 81.0 ° 108.0 ° 202.5 ° 216.0 ° 229.5 ° 270.0 ° - - - - 50 9.0 ° 30.0 ° 90.0 ° 120.0 ° 225.0 ° 240.0 ° 255.0 ° 300.0 ° - - - -

The sizing of the press and the associated flat cam portion depends on the particular industrial constraints to make the tablets at the desired volume.

It may for example be decided to make a press with two outputs (that is to say it is formed two tablets per turn for the same set matrix / punches) so that the flat cam portion must have an angular section necessarily less than 180 °, preferably less than 170 °. The speed of rotation of the press is then adjusted according to the angular section selected for the flat cam portion to have the desired holding time for constant volume compaction.

The dimensioning of the flat cam portion can also be imposed by the operating constraints of the press (limiting rotational speeds). Thus, for a standard production press having a rotation speed of between 18 and 30 revolutions / minute, a flat cam portion having an angular section greater than 3 ° and 5 ° respectively, and preferably greater than 10 °, is used. 18 ° respectively.

If rotational speeds of the press between 18 and 30 rpm are generally preferred to ensure a good rate, it may be necessary to reduce this speed of rotation depending on the composition of the mixture to be compacted, and its behavior at course of compaction. Thus, it is not uncommon for the speed of rotation of the press to be set around around ten revolutions per minute. To maintain an acceptable industrial rate, it is still preferable that the press rotates at a speed at least equal to 5 revolutions / minute, and preferably at a speed greater than 8 revolutions / minute.

Preferably, a planar cam portion having an angular section of between 5 ° and 170 ° is used, which makes it possible to compact mixtures for compaction keeping times of between 100 and 2500 ms, and this according to a wide range of speed of rotation of the press to ensure a good industrial rate. The fact of being able to compact at various speeds of rotation makes it possible to compact any type of mixture during the compaction times indicated (between 100 and 2500 ms), including the mixtures requiring a reduced rotation speed of the press (of the order a dozen revolutions per minute). In addition, the productivity is even better than such an angular section for the flat cam portion also allows to have a press comprising at least two outputs.

Still more preferably, a flat cam portion having an angular section of between 35 ° and 90 ° is used. Such a flat cam makes it possible to compact mixtures during compaction holding times of the order of 800 ms (plus or minus 50 ms) at high rotational speeds of the press. This makes it possible to operate at speeds of between 8 and 18 revolutions / minute, thus offering the possibility of compacting mixtures of various compositions. In addition, it also increases the number of outputs, by putting at least three if desired.

As an illustration of these advantages in terms of productivity, a press with plane compacting cam portions having an angular section of approximately 52 °, makes it possible to configure the press to have two outputs, with about fifty pairs of punches. circulating at the same time in the press, which allows a production of nearly 1100 tablets of coffee per minute (with a speed of rotation of 11 revolutions / minutes, for a compaction time of about 800 ms).

The reader will understand that many changes can be made without materially escaping the new lessons and benefits described here. Therefore, all modifications of this type are intended to be incorporated within the scope of the press device according to the invention.

Claims (10)

1. A press device for manufacturing tablets from a powdery composition comprising at least one powder having elastic properties or thermofusible properties, comprising:

   - a turntable (1) in which is arranged at least one die (2) for receiving the powdery composition,

   - at least one compaction assembly comprising a first punch (3) and a second punch (4), said first and second punches being laid out on either side of the turntable (1) facing the die (2), and being mounted so as to be translationally mobile coaxially with the die (2),

   - first control means (7) and second control means (8) for controlling the axial displacement of the first punch (3) and of the second punch (4) respectively, said first (7) and second (8) control means comprising means co-operating for maintaining the first (3) and second (4) punches in a fixed axial position in which the first (3) and second (4) punches define a confinement volume (V) with the die (2),

   wherein the first control means (7) comprise a first compaction cam (9) for displacing the first punch (3) into the compaction position and the second control means (8) comprise a second compaction cam (10) for displacing the second punch (4) into the compaction position,

   - said first compaction cam (9) comprising a cam path on which said first punch (3) is capable of being displaced, the cam path comprising a first planar portion (90) perpendicular to the axis of the first punch (3),

   - said second compaction cam (10) comprising a cam path on which said second punch (4) is capable of being displaced, the cam path comprising a second planar portion (100) perpendicular to the axis of the second punch (4), the second planar portion (100) extending over an angular section at least equal to the angular section of the first planar portion (90) of the first compaction cam (9) for maintaining the second punch in said die at a fixed compaction axial position at least during said compaction-maintaining time,

   characterized in that the first planar portion (90) extends over an angular section comprised between 5° and 170° for maintaining the first punch (3) in the die (2) at a fixed compaction axial position during a compaction-maintaining time comprised between 100 ms and 2500 ms, the second planar portion (100) extending over an angular section at least equal to the angular section of the first planar portion (90) of the first compaction cam (9) for maintaining the second punch in said die at a fixed compaction axial position at least during said compaction-maintaining time, the first planar portion (90) and the second planar portion (100) being arranged relative to one another so as to maintain, during said compaction-maintaining time, the confinement volume (V) at a constant volume corresponding to the compaction volume for forming the tablet,
   and in that the first punch (3) comprises at least one bearing roller (33) arranged so as to allow both rolling of the first punch (3) on the cam path of the compaction cam (9) according to the direction of rotation of the turntable (1) and an axial displacement of said first punch (3), said bearing roller (33) being laid out at one end of the first punch (3) coaxially with the axis of said first punch (3), with a radial axis of rotation relatively to said first punch (3), and the first punch (3) further comprising a guiding member (34) extending radially relatively to said first punch (3), the first control means (7) comprising at least one guide rail (12) provided with a groove arranged for receiving said guiding member (34).
2. The device of claim 1, wherein the planar portion (90) of the cam path extends over an angular section comprised between 35° and 90°.
3. The device of any one of claims 1 to 2, wherein the cam path of the compaction cam (9) further comprises a pressure rising portion (91) located upstream from the planar compaction-maintaining portion (90), the pressure rising portion (91) being designed so as to axially displace the first punch (3) in the direction of insertion of the first punch (3) into the die (2), towards the axial compaction-maintaining position.
4. The device of any one of claims 1 to 3 wherein the cam path of the compaction cam further comprises a pressure lowering portion located downstream from the planar compaction-maintaining portion (90), the pressure lowering portion being designed for axially displacing the first punch (3) in the direction of withdrawal of the first punch (3) of the die (2), from the axial compaction-maintaining position.
5. The device of any one of claims 1 to 4, wherein the guiding member (34) comprises two rollers (34) laid out on either side of the first punch (3) so as to be able to roll in the grooves laid out on either side of the circular trajectory defined by the displacement of the die (2).
6. The device of any one of claims 1 to 5, wherein the compaction cam (9) comprises at least one stress sensor (C1;C2;C3) positioned in a cavity made in the cam (9) for measuring the stresses undergone by the cam path upon the passing of the first punch (3).
7. The device of claim 6, wherein the compaction cam (9) comprises three stress sensors (C1;C2;C3) distributed in three cavities made in the cam (9), said three cavities being formed at the center and at the two ends of the planar portion (90) of the cam path, respectively.
8. The device of any one of claims 1 to 7, wherein the second control means (8) have a configuration identical with the first control means (7).
9. The device of any one of claims 1 to 8, wherein the second punch (4) has a configuration identical with the first punch (3).
10. The device of any one of claims 1 to 9, wherein the first punch (3) and the second punch (4) respectively correspond to the lower punch (3) and to the upper punch (4) of the press, the first (7) and second (8) control means corresponding to the lower (7) and upper (8) control means, respectively.

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