TABLET PRESS MACHINE AND COMPRESSION METHOD

A rotary tablet press machine comprises a rotating compression turret which includes a die table, provided along a circumferential portion thereof with a plurality of dies, a plurality of first punches and second punches associated with respective dies; a dosing station for dosing high-porosity powdered product in the dies; a compression station provided with a first and a second compression roller adapted to linearly move respectively the first punches and the second punches within the respective dies in order to compress said product and producing tablets; and a compacting station arranged between the dosing station and the compression station and provided with at least one compacting cam adapted to push the first punches and/or the second punches within the respective dies in order to compact the dosed product and allow air in said product to exit.

The present invention relates to tablet press machines for producing tablets, lozenges, pills, for example for pharmaceutical, cosmetic, food, chemical use, by compressing a powdered or granular product. In particular, the invention concerns a rotary tablet press machine and a method for producing tablets in a rotary tablet press machine.

The known rotary tablet press machines typically comprise a compression turret, rotating about a vertical axis and formed by a die table or plate provided with a plurality of dies, i.e. through cavities, angularly distributed equidistant along a circumferential portion of the table and arranged to receive a powdered or granular product dispensed in a apposite dosing station. The turret further comprises a plurality of upper punches and lower punches associated with the respective dies and moved linearly and vertically by cams and compression rollers during the turret rotation.

The lower punches form with the dies seats or housings adapted to receive the product in a dosing station in which the product is inserted in the dies that are closed below by the lower punches. The upper punches and lower punches then compress the inserted product so as to produce the tablets, which are then extracted from the table dies by means of the lower punches that are raised up and afterwards conveyed in an exit chute.

The various manufacturing steps of a tablet are performed during in a single turn of the compression turret which rotates with continuous motion.

The compression of the product in the dies generally occurs in two steps. In a pre-compression station the product is compressed with a limited compression force in order to remove most of the air contained in the product. In a following main compression station the air-deprived product is compressed with high compression force so as to form a tablet. Each pre-compression/compression station comprises an upper compression roller and a lower compression roller, both rotating about horizontal axes and acting respectively on the upper punches and on the lower punches so as to linearly move the punches towards each other within the dies.

The position of the pair of compression rollers, i.e. the distance thereof, is adjustable according to the quantity of product dosed in the dies, the characteristics of the product and above all the amount of compression to be applied on the product in order to obtain tablets having the required dimensions, shape, hardness, porosity.

In order to ensure a high productivity of the tablet press machine and therefore a corresponding high rotation speed of the compression turret, the pre-compression and compression steps must have a very short duration, and this require a quick movement of the upper and lower punches within the dies to compress the product.

In the case of powdered products with high porosity or soft because they contain a significant percentage of air, the high speed with which the upper and lower punches are linearly moved does not allow, also in the pre-compression step, the complete exit from the dies of the air contained in the product. The remaining air does not allow a subsequent correct and homogeneous compression of the powder, since it interferes with the development of the cohesion forces between the solid particles of the powder necessary to form and keep the tablet stable.

To overcome this drawback, it is possible to decrease the movement speed of the punches so as to increase the duration of the pre-compression and compression steps and allow the air to completely exit from the product. Alternatively, it has been proposed to produce punches with larger heads in order to increase the compression time.

However, in both of the aforementioned cases there is a decrease in the productivity of the tablet press machine.

An object of the present invention is to improve the known tablet press machines, in particular rotary tablet press machines having a compression turret provided with dies and punches driven by compression rollers.

Another object is to provide a tablet press machine and a method which allow the optimal compression of soft and/or high-porosity powdered products so as to obtain regular and stable tablets without decreasing the operating speed of the tablet press machine and therefore the productivity thereof.

A further object is to obtain a tablet press machine and a method which allow the complete exit of the air contained in a soft and/or high-porosity powdered product during the tablet formation steps.

In a first aspect of the invention a rotary tablet press machine according to claim1is provided.

In a second aspect of the invention a method for producing tablets according to claim9is provided.

With reference toFIGS.1and2, a rotary tablet press machine1according to the invention is showed, that is arranged to produce tablets, lozenges, pills by compressing a powdered or granular product50for pharmaceutical, cosmetic, food or chemical use and in particular a soft and/or high-porosity powdered product.

The tablet press machine1comprises a compression turret2which is rotating about a vertical rotation axis and which includes a die table3, provided along a circumferential portion or edge thereof with a plurality of dies4, a plurality of first punches5and a corresponding plurality of second punches6associated in pairs with respective dies4and movable to compress a product50introduced in the dies4so as to produce tablets, lozenges or pills.

The dies4are through cavities obtained in the die table3which form, in cooperation with the first and second punches5,6, the seats or housings in which a product50is dosed and subsequently compressed to form the tablets100.

The tablet press machine1comprises a dosing station7arranged to deliver a fixed amount of product50to be compressed within the dies4and at least one compression station8, or main compression station, provided with a first compression roller11and a second compression roller12adapted to respectively drive the first punches5and the second punches6along a compression direction A (FIG.1) within the respective dies4in order to compress the product50delivered in the dies4themselves and obtain the tablets100.

In the embodiment shown inFIGS.1and2, the compression direction A is substantially vertical, i.e. parallel to the rotation axis of the turret2, and the first punches5are the lower punches, while the second punches6are the upper punches. Likewise, the first compression roller11is the lower compression roller acting on the lower punches5and the second compression roller12is the upper compression roller acting on the upper punches6.

The compression station8comprises actuating means of a known type, and therefore not illustrated and described in further detail, acting on the first compression roller11or on the second compression roller12with an settled, almost constant operating force so that the first compression roller11or the second compression roller applies on the first punches5or the second punches6respectively an settled, almost constant compression force.

The compression roller11,12which is not driven by the actuating means is rotatably connected to a support frame of the tablet press machine1.

Each punch of the plurality of first punches5and of the plurality of second punches6has a substantially cylindrical body provided with a respective abutment end5a,6a(or follower end) on which the first compression roller11and the second compression roller12act in contact, which are thus able to impart to the punch the thrust needed to compress the product50within the respective die4.

The rotary tablet press machine1further comprises a compacting station9positioned between the dosing station7and the compression station8and provided with at least one compacting cam13cooperating with the first punches5or the second punches6.

In the compacting station9the abutment ends5a,6aof the first punches5and/or the second punches6are configured to cooperate in contact with the compacting cam13; the latter defines or has a sliding surface13a(or driver profile) on which the abutment ends5a,6aslide in contact so as to push the first punches5and/or the second punches6within the respective dies4, with a predefined compacting force, which is lower than the settled compression force imparted by the first compression roller11and the second compression roller12on the first punches5and/or the second punches6, in order to compact the dosed product50and allow air in the product50to exit.

In the embodiment shown inFIGS.1and2, the compacting cam13is arranged to move the first punches5(lower) along the compression direction A, while the second punches6(upper) remain fixed.

However, in an alternative embodiment of the tablet press machine1of the invention not shown in the figures, it is provided that the compacting cam13is arranged to move the second punches6(upper) along the compression direction A, while the first punches5(lower) are kept fixed.

The compacting cam13is configured to move the first punches5in the compacting station9for a compacting time Tc equal to 10-25 times a compression time Tp in which the first punches5and the second punches6are moved in the compression station8to compress the product50. In this way, during the rotation of the compression turret2at a settled constant speed, the first punches5are moved by the compacting cam13within the dies4with a speed much lower than the speed with which they are moved by the first compression roller11in the compression station8.

The lower speed of the first punches5allows to optimally compact the product50dosed within the dies4since it allows any air in the product to exit, typically if the product is a soft, high-porosity powdered product. During the compacting time Tc the air is in fact capable of exiting through suitable passages provided in the dies and/or punch and not to remain trapped in the product, compromising the subsequent compression operation.

The sliding surface13aor driver profile of the compacting cam13has, for example, a rectilinear profile to give the first punches5a linear motion law.

The compacting cam13is also adjustable along an adjustment direction R, parallel to the rotation axis of the compression turret2, to vary a stroke of the first punches5within the respective dies4i.e. to vary the degree of compacting of the product50according to chemical-physical features thereof (e.g. lower or higher porosity, solid particle size of the powder, cohesion force between the aforementioned particles, etc.).

The compacting station9preferably further comprises a load measuring element14, for example a load cell associated with the compacting cam13and arranged to measure a compacting force applied by the first punches5on the product50contained within the respective dies4.

The load cell14is connected to a control unit30of the tablet press machine1to send data relating to the values of the measured compacting force. The control unit30is configured to receive said data relating to the values of the measured compacting force so as to stop the operation of the tablet press machine1in case of anomalies and/or to adjust the position of the compacting cam13along the adjustment direction R to change the value of the compacting force.

In the embodiment shown inFIGS.1and2, in addition to the compression station8, the tablet press machine1comprises a pre-compression station10interposed between the compacting station8and the compression station9and provided with a first pre-compression roller16acting on the first punches5and a second pre-compression roller17acting on the second punches6.

In the pre-compression station10the product50is compressed at a rapid speed with a limited compression force in order to remove any residual air remaining in the product50after the compacting performed in the previous compacting station9, so that in the compression station8the product50, deprived of air, can be compressed with high compression force and in a reduced compression time Tc and form tablets100having the required dimensional, shape, hardness, porosity characteristics.

In the normal operation of the tablet press machine1of the invention, the compacting station9positioned downstream of the dosing station7, with reference to a rotation direction B of the compression turret2, compacts the product50dosed within the dies4, allowing the almost complete exit of any air in the product50, through apposite passages provided in the dies and/or in the punch(es). In fact, the compacting cam13is configured to move the first punches5within the dies4with a much lower speed than the speed with which the first punches are moved by the first compression roller11in the compression station8since the compacting time Tc available to perform the operation is much longer than the compression time Tp during which the first punches5(and the second punches6) are moved in the compression station8.

The lower speed of the first punches5considerably facilitates the exit of air among the solid particles forming the powder, especially if the powder is soft and/or with high porosity.

In this manner, in the successive pre-compression10and compression8stations the product50, almost free of air, can be optimally compressed so as to obtain tablets, pills, lozenges having settled dimensions, shape, compactness and porosity.

Thanks to the rotary tablet press machine1of the invention provided with a special compacting station9upstream of the compression station8(and any pre-compression station10) with reference to the rotation direction B of the compression turret2, it is therefore possible to optimally compress also soft and/or high-porosity powdered products, i.e. products that are difficult to compress, and obtain regular and stable tablets, without decreasing the operating speed of the tablet press machine1and therefore the productivity thereof. In fact, it is possible, before the compression step, to eliminate almost completely the air contained in the product in the compacting station9.

With reference toFIG.3, a variant of the tablet press machine1of the invention is shown that differs from the embodiment described above and illustrated inFIGS.1and2for the compacting station9which, in addition to the compacting cam13acting on the first punches5(lower), comprises a further compacting cam23arranged to move the second punches6(upper) within the respective dies4.

In this variant of the tablet press machine1both punches5,6are moved in the same die4to compact the product50.

The further compacting cam23has a respective sliding surface23a(or driver profile) adapted to abut a respective abutment end6aof the second punches6and also having a rectilinear profile identical or different from the driver profile13aof the compacting cam13.

The method according to the invention for producing tablets in a rotary tablet press machine1that comprises a rotating compression turret2, which includes a die table3, provided along a circumferential portion thereof with a plurality of dies4, a plurality of first punches5and a corresponding plurality of second punches6associated in pairs with the respective dies4, with the first punches5and the second punches6having a substantially cylindrical body provided with an abutment end5a,6aon which respectively a first compression roller11and a second compression roller12of the tablet press machine act in contact, comprises the steps of:dosing in the dies4a product50, in particular a high-porosity powdered product;compressing the product50dosed in the dies4by moving the first punches5and the second punches6, imparting a settled thrust on the abutment ends5a,6aof the respective first punches5and second punches6by means of contact with the first compression roller11and the second compression roller12in order to compress the product50within the respective dies4so as to produce tablets100; andafter said dosing and before said compressing, compacting the product50dosed in the dies4by applying on the abutment ends5a,6aof the first punches5and/or the second punches6a predefined compacting force carried out by sliding in contact the abutment ends5a,6aalong at least one compacting cam13,23so as to push the first punches5and/or the second punches6within the respective dies4and allow air in the product50to exit.

The method provides compacting the product50in the dies4in a compacting time Tc equal to 10-25 times a compression time Tp during which said compressing is performed.

The method further comprises measuring during the compacting step a compacting force applied by the first punches5and/or the second punches6on the product50within the dies4.

The method further comprises adjusting the compacting force applied by the first punches5and/or the second punches6on the product within the dies4by adjusting the position of the compacting cam13,23, in particular along an adjustment direction R, parallel to the rotation axis of the compression turret2.

The method comprises, after said compacting and before said compressing, pre-compressing the product50in the dies4by moving the first punches5and the second punches6within said dies4.