EP2262638A1

EP2262638A1 - Rotary tablet press comprising a turret having exchangeable parts and method of exchanging parts of the turret

Info

Publication number: EP2262638A1
Application number: EP08719650A
Authority: EP
Inventors: Nicolas Robin; Ivo Van Den Mooter; Koen Van De Voorde; Jurgen Boeckx
Original assignee: GEA Courtoy NV
Current assignee: GEA Process Engineering NV
Priority date: 2008-03-12
Filing date: 2008-03-12
Publication date: 2010-12-22
Also published as: WO2009112886A1; CN102026801A

Abstract

The rotary tablet press (1) comprises a housing (2) including a compression section (6), and a rotary turret (12) including a die disc (15), a top punch guide (29), a bottom punch guide (30) and a spindle (33) defining an axial direction. The turret (12) is positioned in the compression section (6) in a position of use of the rotary tablet press, and may be moved to a removal position. This is achieved by means of quick separation means allowing separation of at least the top punch guide (29) from the die disc(15) and the bottom punch guide (30) in the compression section (6) following which the die disc(15) and/or other parts may be moved out of the compression section (6).

Description

Rotary tablet press comprising a turret having exchangeable parts and method of exchanging parts of the turret

Field of the invention The present invention relates to a rotary tablet press comprising a housing including a compression section, and a rotary turret. The invention furthermore relates to a method of exchanging parts of the turret.

Background of the invention

In such a rotary tablet press, the turret is positioned in the compression section in a position of use of the rotary tablet press, i.e. when the tablet press is in working operation. The turret comprises a number of parts including a die disc or a die disc portion. The die disc is secured between the top punch guide and the bottom punch guide. Alternatively, the die disc portion is integral with the top and/or bottom punch guide in a one-part or two-parts turret. The turret is driven in rotation by means of a spindle coupled to driving means and the entire turret thus rotates during operation. A powder or granular material is fed to the rotary tablet press. The rotation entails, i.a., that the punches accommodated in the top and bottom punch guides are reciprocated to compress the material to tablets. In order to carry out a change-over in the production, e.g. from one material to another or from one tablet size or shape to another, the entire turret is traditionally removed in order to clean the turret or to replace the punches and dies in the turret. As an alternative, only dies accommodated in the die disc may be exchanged when the turret is still located in the compression section, which is a relatively complicated procedure. Furthermore, other parts of the turret may need to be exchanged with the turret in place, such as for instance the punches.

Hence, these operations are relatively complicated and/or time- consuming in themselves, thus leading to a relatively long change-over time when the need for replacement and/or cleaning any of the parts of the turret arises. In order to exchange the die disc of the turret, the prior art has suggested to divide the die disc into a number of segments, each segment including a number of dies or bores. However, also this solution has a number of drawbacks: Secure coupling of the segments to each other and to the turret requires handling of clamping bolts and wedges. This increases the change-over time from one tooling set/one tablet shape to another. Furthermore, the cleaning time for a segmented die table is increased due to the configuration of the segments. The extra amount of work to be carried out in connection with a number of segments is even more pronounced, when regrinding the die disc surface when scratched or otherwise damaged. Furthermore, it is also quite difficult and hence quite expensive to produce the die segments, to such a narrow/high tolerance that they can be positioned/installed on the turret, so that the die bores coincide with the top and bottom punch bores. This is partly due to the fact that very high tolerances are required, both on the turret and die segments, to make sure assure correct levelling of the segments.

Summary of the invention With this background it is an object of the present invention to provide a rotary tablet press of the kind mentioned in the introduction, by which ease of operation is obtained.

This and further objects are achieved by a rotary tablet press comprising a housing including a compression section, and a rotary turret including a die disc, a top punch guide, and a bottom punch guide, said turret defining an axial direction and being positioned in the compression section in a position of use of the rotary tablet press, said die disc being secured between said top punch guide and said bottom punch guide in the position of use, characterized in that quick separation means are provided for allowing quick separation between the die disc and the top punch guide and/or between the die disc and the bottom punch guide in the compression section to attain a removal position.

In this manner, the time-consuming dismounting and subsequent removal of the entire turret from the compression section of the rotary tablet press is made redundant if only for instance a single part is to be exchanged. The three main parts of the turret, i.e. top punch guide, die disc and bottom punch guide, may be separated from each other and removed from the compression section independently of each other, once the removal position is attained. By allowing a quick removal of any of these parts, this part or these parts can be easily exchanged when the part or parts is/are worn. Further, the change from one tooling type or size to another is facilitated as the bottom punch guide and the die disc may be removed from the compression section and exchanged for other types, whereas the top punch guide may be left in the compression section while its bushings are exchanged for other ones. Furthermore, it is possible to make use of a one-piece die disc without the disadvantages of the segmented die discs, and exchange of the die disc may easily take place with the remaining parts still located in the compression section. Furthermore, the invention provides for a more robust and operator-friendly exchange of the parts, including the top punch guide, the die disc and the bottom punch guide, the exchange thus requiring no loose parts for installing and removing the part or parts, and, in principle, can be tool-free when using manual installation. All in all, these measures provides for a very advantageous change-over procedure reducing the downtime to a considerable extent. In particular in the case when the die disc is to be exchanged, a further die disc may be prepared in order to replace the previous die disc as soon as it has been taken out of the tablet press. In an embodiment, the quick separation means are adapted for allowing quick separation between the die disc and at least the top punch guide by release means and lifting means. This provides for a limited number of operational steps to be carried out in order to separate the top punch guide from the die disc and the bottom punch guide, viz. two steps, the first step being release of the engagement, and the second step being lifting the top punch guide from the die disc and the bottom punch guide. Furthermore, this embodiment is particularly advantageous if convenient removal of the top punch guide only from the compression section is aimed at. This is particularly advantageous in case the rotary tablet press is of the kind, in which the top punches leave the dies once per revolution, and in which a tight fit between the top punch guide bores and the top punches is consequently required. In turn, this entails that the top punch guide bores are worn more rapidly than the bottom punch guide bores, and replacement of the entire top punch guide or possibly the bushings in the top punch guide bores is necessary.

In a preferred embodiment, the turret includes a spindle extending in said axial direction through the top punch guide, the die disc and the bottom punch guide in the position of use, and said quick separation means comprise spindle release means located within said turret and adapted to release and move the spindle axially, and lifting means adapted to lift at least the top punch guide and the spindle out of engagement with the die disc and the bottom punch guide to attain said removal position. The location of the spindle release means within the turret itself makes the arrangement particularly compact and manageable. Furthermore, this reduces the need for external tools for releasing and moving the spindle axially.

In a development of this preferred embodiment, the spindle release means of said quick separation means include a detachable connection between the spindle and the bottom punch guide, a first spring and a second spring, the first spring being accommodated in the top punch guide, the upper end of said first spring abutting against a slider element, and the second spring being accommodated in said slider element, the upper end of said second spring abutting against an upper portion of the spindle, the first spring being adapted to provide a preload on said slider element, and said second spring being adapted to provide a preload on said spindle. The use of springs provide for a mechanically reliable operation of the spindle release means.

In a further development, the second spring is adapted to move the spindle axially to a position in which the lower end of spindle is positioned within the bottom punch guide, the travel of the spindle being limited by an enlarged section on said spindle being brought into abutment with a shoulder portion on said slider element and/or a pin of the spindle being brought into contact with a nut element connected to the bottom punch guide. The limitation of the spindle travel makes it possible to define intermediate positions during separation of the top punch guide from the die disc and the bottom punch guide.

Preferably, also the second part of the travel includes a limita- tion, as the first spring is adapted to move the spindle axially into said removal position, the travel of the spindle being limited by a shoulder portion on the slider element being brought into abutment with a shoulder portion on an element connected to the top punch guide.

In order to ease manufacture and assembly of the rotary tablet press the slider element may constitute a second slider element connected to a first slider element. In this manner the second spring may easily be positioned within the second slider element, following which the first slider element is connected to the second slider element, thus locking in the second spring. The spindle may be secured to a clamping device. This allows for a particularly easy operation during the initial phase of separating the top punch guide from the die disc and the bottom punch guide.

In an alternative embodiment, the turret includes a spindle extending in said axial direction through the bottom punch guide only in the position of use, and said quick separation means comprises release means for separating the top punch guide from the die disc and the die disc from the bottom punch guide and lifting means for lifting the top punch guide out of engagement with the die disc and the bottom punch guide to attain said removal position. In a further development of this alternative embodiment, the means for separating the top punch guide from the die disc and the die disc from the bottom punch guide include bolts or a quick lock mechanism.

In a further embodiment, the turret furthermore comprises a number of guide pins accommodated in bores in the top punch guide, the die disc and the bottom punch guide, respectively. The guide pins provide for an excellent clamping and alignment of the parts of the turret with respect to each other, and a reliable transferral of the torque from the drive shaft to the parts of the turret is achieved. Preferably, the guide pins and the bores are slightly conical, which provides for at tight fit and increases the correctness of the alignment and torque transferral even further.

In order to facilitate the removal of the die disc, the quick sepa- ration means may furthermore comprise a plurality of spring-loaded push pins accommodated in the bottom punch guide, said spring-loaded push pins being adapted to lift the die disc slightly.

In an embodiment providing for an even further enhanced alignment the turret furthermore comprises at least one alignment pin accommodated in the bottom punch guide and cooperating, in the position of use, with an alignment bore provided in the die disc.

In case the rotary tablet press is provided with such an alignment pin and spring-loaded push pins, the spring-loaded push pins are preferably adapted to lift the die disc, in the removal position, to such an extent that the alignment bore is lifted up over the alignment pin.

Alternatively, the quick separation means are adapted for allowing quick separation between the die disc and the bottom punch guide by release means and lifting means.

In order to make the removal of parts of the turret from the compression section even easier, the die disc preferably has a reduced weight, preferably below 10 kg.

The weight reduction may for instance be obtained by forming the die disc of a lightweight material, such as a lightweight metal or metal alloy. Alternatively, or additionally, the die disc may be designed as a ring. Further measures for reducing the weight include providing the die disc with a plurality of bores and/or milled profiles.

Although the die disc may, in principle, be removed from and inserted into the compression section manually, the rotary tablet press preferably furthermore comprises a die disc removal device in the compression section of the housing.

In one embodiment, said die disc removal device comprises a vertical pillar to which a swivel arm is connected pivotally.

The swivel arm may have a first and a second leg adapted to be inserted below the die disc. Alternatively, the swivel arm has a substantially C-shaped leg adapted to be inserted below the die disc.

In another embodiment, said die disc removal device comprises a vertical pillar to which a horizontal arm is secured, and wherein a carriage capable of translatory movement is connected to the horizontal arm, said carriage being, in turn, connected to a first and a second leg adapted to be inserted below the die disc.

Alternatively, said die disc removal device comprises a translatory carriage connected to a stationary plate in the compression section by means of fittings, said translatory carriage comprising a plurality of bearings and guide plates on either longitudinal side

In a further aspect of the invention, a method of exchanging at least one part of the turret of a rotary tablet press is provided. The method comprises the steps of: providing quick separation between the die disc and the top punch guide and/or between the die disc and the bottom punch guide in the compression section to attain a removal position, removing said at least one part from the compression section, and inserting a part into the compression section.

Brief description of the drawings

In the following the invention will be described in further detail by means of examples of embodiments and referring to the schematic drawings, in which Fig. 1 shows a perspective view of a rotary tablet press according to the invention;

Fig. 2 is a view similar to that of Fig. 1 showing the rotary tablet press of Fig. 1, however with some details in another position;

Fig. 3 is a view similar to that of Fig. 1 showing the rotary tablet press of Fig. 1, however with some details in yet another position;

Fig. 4 is an axial section of a detail of the rotary tablet press;

Fig. 5 is an axial section of a detail of the rotary tablet press corresponding to the position shown in Fig. 2;

Fig. 6 is an axial section of a detail of the rotary tablet press corresponding to the position shown in Fig. 3;

Figs 7 and 8 are partial perspective views showing one example of a method of exchanging a die disc;

Figs 9 and 10 are partial perspective views showing another example of a method of exchanging a die disc;

Figs 11 and 12 are partial perspective views showing a further example of a method of exchanging a die disc;

Figs 13 and 14 are partial perspective views showing a still further example of a method of exchanging a die disc; Fig. 15 is a sectional perspective view of a detail of an alternative embodiment of the rotary tablet press; and

Fig. 16 is a view corresponding to Fig. 6 of a detail of a further alternative embodiment of the rotary tablet press.

Detailed description of the invention and of preferred embodiments

Fig. 1 shows a rotary tablet press 1 for compression of a feedstock in the form of powder or granular material into tablets, compacts or the like. The press shown is of a type suitable for use in the pharmaceutical industry, but the press according to the invention may as well be a so-called industrial press employed in the production of a variety of different products, such as vitamins, nutritional supplements, food, pet food, detergents, salts, explosives, ceramics, batteries, balls, bearings, nuclear fuels, etc.

The rotary tablet press 1 has a press housing 2 comprising a frame 3 and an outer lining 4. The press housing 2 is composed of three sections, which are located on top of each other and are separated by means of partition walls. The lower section, designated the drive section 5, is separated from a central section, designated the compression section 6, by a bottom frame 7 of the press, and the compression section 6 is separated from an upper section, designated the accessory section 8, by a top frame 9 of the press. There is an outer lining over the upper section 8 as well (not indicated as such). The bottom and top frames 7 and 9 with a bottom plate (not shown) and two vertical support rods 7a and 7b (shown in Fig. 1 only) extending between the bottom and the top frame form the press structure

The drive section 5 comprises a not shown electrical drive motor having a suitable transmission for driving a vertical drive shaft 10 (cf. Fig. 4) projecting up through a central opening in bottom frame 7 and having at its upper end a coupling part 11 for detachable connection with a rotary turret 12 located in the compression section 6 of the press housing 2 in a position of use of the rotary tablet press 1. As shown in Fig. 1, a drive shaft guide frame 13 covers the portion of the drive shaft 10 protruding above the bottom frame 7. During use of the rotary tablet press 1, the compression section

6 is covered by a number of wall elements or windows 14 of which at least some may be transparent. In Fig. 1, the wall elements 14 are shown in raised position.

Referring to Fig. 4, the rotary turret 12 comprises, in the em- bodiment shown, three main parts, viz. a plate-shaped element designated a die disc 15 formed as a one-piece disc, a top punch guide 29 and a bottom punch guide 30. In the embodiment shown, the die disc 15 has a number of bores 16 fulfilling the function as dies, i.e. forming the tablets to the desired shape and size. The bores 16 are arranged evenly distributed along its circumference, each bore 16 being arranged with its axis parallel to the vertical rotational axis of the turret 12. The use of traditional dies is also conceivable. The dies may be of any suitable kind and include any suitable tensioning device for retaining them in the die disc. For instance, the tensioning device may provide a substantially circumferential pressure on the die, thus making it possible to utilize productivity increasing dies having a thin wall thickness. Such a tensioning device and dies are devised in Applicant's co-pending international application filed on the same day as the present application. On either side of the die disc 15 are arranged top and bottom punches 17, 18, respectively, in corresponding guide bores 19, 20 formed in the top punch guide 29 and the bottom punch guide 30, respectively. The punches 17, 18 are accommodated in the turret 12 so that a first end of each punch 17, 18 is able to enter a corresponding bore 16 by displacement of the punch in its guide bore 19, 20 in order to compress material in the bore 16. The punches 17, 18 may be sealed against their guide bores 19, 20 at the end of these facing the die disc 15 by means of not shown lip seals. For use with toxic or higly active products, a bellows seal, for instance of silicone, may be employed. A second end of each punch 17, 18 is in a well-known manner co-operating with top and bottom cams, respectively, arranged stationary in relation to the press housing 2 in order to effect axial displacement of the punches by rotation of the turret 12. The cams only extend along part of the circumference of the turret, and at that circumferential position where the final compression of the material in the bore or die is to be performed, top and bottom precompression rollers and top and bottom main compression rollers, respectively, take over the displacement of the punches 17, 18.

The rotary tablet press 1 is provided with a feeding device in the form of a not shown, well-known double rotary feeder with two rotary paddles located in a feeder housing and driven by means of separate drive motors located in the accessory section 8 of the press housing 2. The feeding device has been removed in the figures for the sake of simplicity. The rotary tablet press 1 is further provided with a not shown tablet chute protruding from the compression section 6 for conducting away compressed material in the form of tablets from the bores 16.

Further, means may be provided for extracting dust to a not shown, well-known, suction system. In order to clean the interior of the compression section 6 between batches of different products or in order to exchange the unit for another type of unit, the rotary tablet press 1 shown in Fig. 1 is equipped with a handling system for removal of the entire turret 12 from the press and for placement of another turret 12 in the press. As in a traditional rotary tablet press, the handling system comprises lifting means in the form of a swivel arm 51 (cf. Fig. 2) pivotally journalled about the axis of a vertical pillar 50 of the frame 3. By means of the swivel arm 51 the entire turret 12 may be moved from its position of use shown in Fig. 1 to a turret removal position shown in Fig. 2 by swinging out swivel arm 51 and hence the turret 12 to a position where the turret 12 may be set off on a carriage (not shown) for transferral to a cleaning or exchange station, for instance. It is noted that the term "removal" is used for any action involving movement of the part in question out of the compression section. The term "exchange" is used for describing actions involving removal and/or insertion of the same or a different part out of and/or into the compression section.

Prior to swinging out the turret 12, the parts of the turret 12 are moved from their working position corresponding to their position of use shown in Fig. 4 to the position shown in Fig. 5 corresponding to the above-mentioned turret removal position, in which the turret 12 is free to swing out of the compression section 6 of the press. The operations carried out in this respect will be described with reference to these figures. As mentioned in the above the turret 12 comprises a top punch guide 29 and a bottom punch guide 30 positioned on either side of the die disc 15. The top punch guide 29 accommodates, on its upper side, a top cam 31, on top of which a disc 32 abuts. Each of these parts is provided with a central bore or aperture for receiving a through-going spindle 33 having an upper portion 33a and a lower portion 33b. At a position between the upper and lower portions 33a, 33b, the spindle 33 has an upper enlarged section 34a, which may e.g. be an O-ring, and a pin 34b, the function of which will be described in further detail below.

A plurality of elements surrounds the spindle 33 coaxially: A clamping device 35; a first slider element 36; and a second slider element 37. Furthermore, a nut element 28 is firmly connected to the bottom punch guide 30. Whereas the clamping device 35 is secured to the spindle 33 so that these two parts may be moved together in the axial direction, the first and second slider elements 36, 37 slidable relative to the clamping device 35 and the spindle 33, i.e. the spindle 33 may be moved relative to the first and second slider elements 36, 37 in the axial direction. In turn, the first and second slider elements 36, 37 are slidable also relative to the other parts of the turret 12. This will be described in further detail below. The clamping device 35 is of a kind known per se and will not be described in further detail.

Furthermore, the turret 12 is provided with a first spring 38 and a second spring 39. The first spring 38 is accommodated in the top punch guide 29 and its upper end abuts against the second slider element 37, and the second spring 39 is accommodated in the second slider element 37 and its upper end abuts against the upper portion 33a of the spindle 33. The springs 38, 39 are compression springs that are compressed in the position shown in Fig. 4, i.e. they provide a preload on the second slider element 37 and the spindle 33, respectively. In the area forming the transition between the die disc 15 and the bottom punch guide 30, the turret 12 is provided with an alignment pin 22 accommodated in the bottom punch guide 30 and cooperating, in the shown working position of Fig. 4, with an alignment bore 23 in the die disc 15. The alignment pin 22 ensures correct alignment between the bottom punch guide 30 and the die disc 15. Furthermore, a plurality of push pins is accommodated in the bottom punch guide 30. In Figs 4 to 6, only a single push pin 24 is shown. The push pin 24 is loaded in the upwards direction by a spring 25. The other, not-shown push pins distributed over the bottom punch guide 30 are spring-loaded in a similar manner. The function of the spring-loaded push pins 24 will be described in further detail below.

Eventually, the turret 12 is provided with a number of guide pins 40 accommodated in bores 41, 42 and 43 in the top punch guide 29, the die disc 15 and the bottom punch guide 30, respectively. Although not clearly visible, these guide pins 40 are slightly conical, e.g. 1 :50, and the bores 41, 42 and 43 are formed with a similar conicity. This provides for a tight fit between each guide pin 40 and the corresponding bores 41, 42 and 43. In turn, this enhances the proper alignment between the bottom punch guide 30, the die disc 15 and the top punch guide 29. This is particularly important as the guide pins 40 transmit the torque from the drive shaft 10 via the coupling part 11 and the bottom punch guide 30 to the die disc 15 and the top punch guide 29. Although not preferred, cylindrical pins may be utilized as well.

As an alternative, the turret may, in a not-shown embodiment, include a spindle extending in the axial direction through the bottom punch guide only in the position of use, the quick separation means comprising means for separating the top punch guide from the die disc and the die disc from the bottom punch guide. Such quick separation means may be formed in any manner conceivable to a person skilled in the art. For instance, the means for separating the top punch guide from the die disc and the die disc from the bottom punch guide may include bolts or a quick lock mechanism. The term "quick separation" is intended to be interpreted as including only few operational steps in order to provide the removal position. In the embodiment shown below, the quick separation means include release means and lifting means. The quick separation aimed at is thus achieved in only two main operational steps. Arrangements involving simultaneous release and lifting, i.e. a one-step quick separation, or a slightly larger number of operational steps also fall within the frames of the definition of the term "quick separation means". The number of operational steps may e.g. be lower than 10, preferably lower than 5. Advantageously, the quick separation means needs only few devices to be operated in order to achieve the release and the lifting. In order to move the turret 12 from its normal working position shown in Fig. 4 to the position shown in Fig. 5, i.e. the turret removal position, the clamping device 35, the spindle 33 and the first and second slider elements 36, 37 are lifted, i.e. moved upwards in the axial direction. In the embodiment shown, this is carried out by releasing the spindle 33 from its engagement with the coupling part 11, which in turn allows the first spring 38 to move towards its relaxed state while exerting an upwards directed force on the second slider element 37. This force is transmitted, via the first slider element 36, to the clamping device 35 and thus to the spindle 33. Hence, during this operation the spindle 33 is lifted out of engagement with the coupling part 11 with assistance from the spring-load of the first spring 38 until a shoulder portion 37a on the second slider element 37 comes into abutment with a corresponding shoulder portion 32a on the disc 32. As may be seen, the pin 34b of the spindle 33 is brought into contact with the nut element 28. When the spindle 33 has thus reached the end of its travel, the swivel arm 51 is brought into engagement with the first slider element 36. Following this, the entire turret 12 is lifted by the lifting means in the form of vertical pillar 50 and swivel arm 51 and may be swung out of the compression section 6 to attain the position shown in Fig. 2. Alternatively, the entire lifting operation could be carried out by means of not shown lifting means in the accessory section 8 of the press.

The rotary tablet press 1 according to the invention provides for the further possibility of removing not only the entire turret 12 as described in the above, but also of the main parts of the turret 12 individually, i.e. independently of each other. In the following, the removal of the die disc 15 alone will be described in detail. In the position shown in Fig. 3 the die disc 15 is in a removal position, in which it is possible to remove i.a. the die disc 15 from the remaining parts of the turret 12. This removal position will thus be referred to as being a die disc removal position. However, removal of the other main parts, i.e of the top punch guide 29 and the bottom punch guide 30, is of course conceivable. Referring now to Figs 4 and 6 the operations necessary to attain the die disc removal position will be described in detail. These operations thus entail quick separation of at least the top punch guide 29 from the die disc 15 and the bottom punch guide 30 in the compression section 6 to attain a die disc removal position. The quick separation means allowing this separation comprise spindle release means located within the turret 12 and adapted to release and move the spindle 33 axially, and lifting means adapted to lift at least the top punch guide 29 and the spindle 33 out of engagement with the die disc 15 and the bottom punch guide 30 to attain the die disc removal position. In the embodiment shown, the lifting means comprise the vertical pillar 50 and the swivel arm 51, but other arrangements are of course conceivable. First, the spindle 33 is released from its engagement with the coupling part 11 by unscrewing the lower portion 33b of the spindle 33 by turning a nut (not shown in detail) of the clamping device 35. The second spring 39 is now allowed to move towards its relaxed state while exerting an upwards directed force on the spindle 33 at the upper portion 33a thereof. The first part of the travel of the spindle 33 thus takes place with assistance from the spring-load of the second spring 39, and ends when the upper enlarged section 34a is brought into abutment with a lower shoulder portion 37b on the second slider element 37. Simultaneously, the clamping device 35 and hence the spindle 33 are moved relative to the slider elements 36 and 37. At the end of this first part, the pin 34b of the spindle 33 has been brought into contact with the nut element 28. In principle, the cooperating pin 34b and the nut element 28 may have any suitable form, as long as they allow for movement between two positions, i.e. one in which they prohibit upwards axial movement of the spindle 33, and one in which they allow such upwards axial movement.

Second, and following this operation, the spindle 33 is released from its engagement with the bottom punch guide 30 by disengaging the pin 34b from the nut element 28. This is obtained by turning the spindle 33 until the pin 34b is in a position to move past the nut element 28. As in the above description of the turret removal, the spindle 33 and the clamping device 35 are lifted with assistance from the spring-load of the first spring 38 until the shoulder portion 37a on the second slider element 37 comes into abutment with the corresponding shoulder portion 32a on the disc 32.

Third : When the spindle 33 has thus reached the end of its travel, the swivel arm 51 is brought into engagement with the first slider element 36. The clamping device 35 and the spindle 33 are lifted, i.e. moved upwards in the axial direction, thus lifting the spindle 33 out of engagement with the coupling part 11. Simultaneously, the top punch guide 29 and other parts of the turret 12 situated above the die disc 15 are lifted upwards, leaving the die disc 15 and the bottom punch guide 30 in contact with the drive shaft 10 and the coupling part 11. In particular it is noted that the guide pins 40 are lifted out of engagement with the bores 42, 43 in the die disc 15 and the bottom punch guide 30, respectively, in the position shown in Fig. 6. When the top punch guide 29 and the other parts situated above the die disc 15 have thus been lifted, each push pin 24 is urged upwards by the spring 25. The combined upwards directed force exerted by the push pins 24 lifts the die disc 15 slightly above the bottom punch guide 30 such that the alignment bore 23 is brought out of engagement with the alignment pin 22. When the upper parts of the turret 12 have been lifted, the position shown in Figs 3 and 6 is attained, i.e. the die disc removal position. In principle, the swivel arm 51 could be swung out to leave the die disc 15 uncovered and free to be removed, e.g. lifted manually, in order to clean or exchange the die disc for another one. This method of exchanging the die disc is preferred for a number of reasons: It requires no tools at all, apart from the ones already present in the rotary tablet press 1, which renders the overall arrangement less expensive. Furthermore, under normal circumstances it will be faster than removal and re-insertion making use of tools. Obviously, this sets a limit on the weight of the die disc 15. However, it has turned out that it is possible to provide die discs having a weight of approximately 10 kg or below as described in further detail in connection with the embodiment shown in Fig. 15.

However, as an alternative the invention provides for embodi- ments of devices for removing the die disc 15 from the turret 12 situated in the compression section 6, exchanging the die disc 15 for another one, alternatively cleaning the same die disc 15, and reinstating another die disc or the same die disc 15 into the turret 12.

Figs 7 and 8 show an embodiment, in which a die disc removal device comprises a vertical pillar 60 on which a fork-like arrangement is provided : A swivel arm 61 connected pivotally to the vertical pillar 60 has a first and a second leg 62 and 63, respectively, which may be inserted on either side of the central portion of the die disc 15. Following this, the swivel arm 61 is moved about an axis coinciding with that of the vertical pillar 60 to attain the position shown in Fig. 8. As may be seen, the remaining parts of the turret 12 are kept in place in the compression section 6, viz. the bottom punch guide 30 on the coupling part 11 (not visible in this figure), and the top punch guide 29 and other parts situated above the die disc 15 in the working position of the turret 12 suspended in e.g. the swivel arm 51 mounted on the vertical pillar 50 as described in the above. Following this operation, the die disc 15 may be moved to a cleaning or exchange station. Subsequently, the same die disc 15 or another die disc is placed on the first and second legs 62, 63, and the swivel arm 61 is swung into the compression section 6 again.

Figs 9 and 10 show another embodiment making use of rotational removal movement for moving the die disc 15 out of and into the compression section 6. Only differences relative to the above-mentioned embodiment of Figs 7 and 8 will be described. In this embodiment a vertical pillar 160 is mounted on the vertical pillar 50 and the swivel arm 161 holds a substantially C-shaped leg 162 for holding the die disc 15 during the entire exchange operation, i.e. during removal of the die disc 15 from the compression section 6 and insertion of the same die disc 15 or another die disc into the compression section 6. In the embodiment shown in Figs 11 and 12, the die disc removal device comprises a vertical pillar 70 on which a horizontal arm 71 is secured. On the horizontal arm 71 a carriage 72 capable of translatory movement along the horizontal arm 71 is provided. The carriage 72 is, in turn, connected to a first and a second leg 73 and 74, respectively, which may be inserted on either side of the central portion of the die disc 15. Following this, the carriage 72 is moved out of the compression section 6 along the horizontal arm 71 to attain the position shown in Fig. 12. As in the above embodiment of Figs 7 and 8, the remaining parts of the turret 12 are kept in place in the compression section 6, and the die disc 15 may be handled as described in the above.

A further embodiment making use of translatory movement is shown in Figs 13 and 14. In this embodiment, the die disc removal device comprises a translatory carriage 170 connected to a stationary plate 52 in the compression section 6 by means of fittings 171. The translatory carriage 170 comprises a plurality of bearings 172 and guide plates 173 on either longitudinal side. The die disc 15 is thus moved from the position shown in Fig. 13 along the translatory carriage 170 on the bearings 172 and guided by the guide plates 173 to attain the position shown in Fig. 14. As in the above embodiment of Figs 7 and 8, the remaining parts of the turret 12 are kept in place in the compression section 6, and the die disc 15 may be handled as described in the above.

When re-inserting the die disc 15 or another die disc into the compression section 6, the operations described in the above with reference to Figs 4 and 6 are carried out in substantially reversed order.

That is, when the die disc 15 has been positioned on top of the bottom punch guide 30, for instance by means of any one of the die disc removal devices described in the above, the top punch guide 29 and the other parts of the turret 12 are first of all lowered until the top punch guide 29 abuts on the die disc 15. Then, first and second sliders 36 and 37 are moved axially downwards against the spring-load of the first spring 38. Finally, clamping device 35 and spindle 33 are moved downwards against the spring-load of the second spring 39. During this final part, the pin 34b is moved past the nut element 28, and eventually the lower portion 33b of the spindle 33 is screwed into the coupling part 11 again.

In the alternative embodiment of the turret shown in Fig. 15 turret elements having the same or analogous function as turret elements in the embodiment of the rotary tablet press shown in Figs 4 to 6 carry the same reference numerals to which the sign ' has been added. Only differences relative to the earlier embodiment will be described in detail.

Preferably, the die disc of the rotary tablet press according to the invention has a reduced weight of below 10 kg. This may be achieved by forming the die disc of a suitable lightweight material, such as a lightweight metal or metal alloy, for instance titanium or aluminium. In the embodiment shown the weight is reduced by forming the die disc 15' as a ring of any material, for instance hardened steel. If an even larger weight reduction is desired, it is of course conceivable to design the ring-shaped die disc 15' of a lightweight material. Furthermore, the die disc 15' may be provided with additional bores (dummy bores) and/or milled profiles to reduce the weight even further.

The ring-shaped die disc 15' has an extension in the radial direction limited by an inner periphery 15a' and an outer periphery 15b', thus providing the die disc 15' with a volume that is substantially reduced in comparison with a die disc having a small aperture only. The punch receiving bores or dies are of course located within the area delimited by the inner and outer peripheries 15a' and 15b'. The inner periphery 15a' is designed as a protruding portion having the function of centring the die disc 15a' with respect to the turret 12', viz. by abutment against a shoulder portion 29a' on the top punch guide 29'. At some points along the inner periphery 15a', the die disc 15' is in engagement with an element 44', which may be one of a number of such elements. In the embodiment shown and described, element 44' is a quarter-turn quick lock device that locks the die disc 15' to the bottom punch guide, to keep the die disc 15' in place, when the top punch guide is lifted. After swivelling away the top punch guide, one can access the quarter turn, unlock the die disc 15' from the bottom punch guide, and remove the die disc 15', with the aid of the push pins. However, other suitable quick lock devices are of course conceivable to the person skilled in the art.

Another difference from the embodiment shown in Figs 4 to 6 is that the lower portion 33b' of the spindle 33' is coupled directly to the drive shaft 10', that is, the coupling part 11 of the earlier embodiment is not present in the embodiment of Fig. 15.

The parts of the turret 12' of the embodiment of Fig. 15 may be exchanged as described in the above with reference to Figs 1 to 14.

In the further alternative embodiment of the turret shown in Fig. 16 turret elements having the same or analogous function as turret elements in the embodiment of the rotary tablet press shown in Figs 4 to 6 carry the same reference numerals to which the sign " has been added. Only differences relative to the earlier embodiment will be described in detail. In contradistinction to the embodiment of Figs 1 to 6, the die disc 15" is still in engagement with the top punch guide 29" when the removal position shown in Fig. 16 is obtained, i.e. when the die disc 15" has been brought out of engagement with the bottom punch guide 30" by quick separation means including release means and lifting means. The quick separation means work, in substance, as in the embodiment of Figs 1 to 6 with the exception that the die disc 15" follows the top punch guide 29" when lifting the top punch guide 29" in order to attain the removal position shown in Fig. 16. The parts will not be described in further detail, as a person skilled in the art will be capable of devising parts suitable to the purpose.

Furthermore, an extra die disc may be prepared in advance outside the rotary tablet press, while the press is in operation with an already mounted die disc. When exchange is decided upon, the rotary tablet press is stopped, and the mounted die disc is removed. The extra die disc is then mounted in the turret. The change-over time is then reduced to a significant degree. In order to allow preparation of die discs including dies adapted for the manufacture of shaped tablets, the dies need to be aligned in order to ensure correct introduction of the top punches into the aperture of the die. This may be carried out by a tool constituting a dummy top punch guide which is positioned opposite the upper side of the die disc with the dies positioned in the corresponding bores, however before the tightening of the tensioning device. When the complete turret 12 is subsequently installed, then the bottom punches are installed. During this operation the bottom punches are oriented by the dies/die bores themselves.

The invention is not limited to the embodiments shown and described in the above. Several combinations and modifications may be carried out without departing from the scope of the appended claims.

Claims

P A T E N T C L A I M S

1. A rotary tablet press (1) comprising a housing (2) including a compression section (6), and a rotary turret (12) including a die disc (15), a top punch guide (29), and a bottom punch guide (30), said turret defining an axial direction and being positioned in the compression section (6) in a position of use of the rotary tablet press, said die disc (15) being secured between said top punch guide (29) and said bottom punch guide (30) in the position of use, c h a r a c t e r i z e d in that quick separation means are provided for allowing quick separation between the die disc (15) and the top punch guide (29) and/or between the die disc (15) and the bottom punch guide (30) in the compression section (6) to attain a removal position.

2. A rotary tablet press according to claim 1, wherein the quick separation means are adapted for allowing quick separation between the die disc (15) and at least the top punch guide (29) by release means and lifting means.

3. A rotary tablet press according to claim 2, wherein the turret (12) includes a spindle (33) extending in said axial direction through the top punch guide (29), the die disc (15) and the bottom punch guide (30) in the position of use, and the release means of said quick separation means comprise spindle release means located within said turret (12) and adapted to release and move the spindle (33) axially, and lifting means (50,51) adapted to lift at least the top punch guide (29) and the spindle (33) out of engagement with the die disc (15) and the bottom punch guide (30) to attain said removal position.

4. A rotary tablet press according to claim 3, wherein the spindle release means of said quick separation means include a detachable connection between the spindle (33) and the bottom punch guide (30), a first spring (38) and a second spring (39), the first spring (38) being accommodated in the top punch guide (29), the upper end of said first spring (38) abutting against a slider element (37), and the second spring (39) being accommodated in said slider element (37), the upper end of said second spring (39) abutting against an upper portion (33a) of the spindle (33), the first spring (38) being adapted to provide a preload on said slider element (37), and said second spring (39) being adapted to provide a preload on said spindle (33).

5. A rotary tablet press according to claim 4, wherein the second spring (39) is adapted to move the spindle (33) axially to a position in which the lower end (33b) of spindle is positioned within the bottom punch guide (30), the travel of the spindle (33) being limited by an enlarged section (34a) on said spindle (33) being brought into abutment with a shoulder portion (37b) on said slider element (37) and/or a pin (34b) of the spindle (33) being brought into contact with a nut element (28) connected to the bottom punch guide (30).

6. A rotary tablet press according to claim 5, wherein the first spring (38) is adapted to move the spindle (33) axially into said removal position, the travel of the spindle being limited by a shoulder portion (37a) on the slider element (37) being brought into abutment with a shoulder portion (32a) on a disc (32) connected to the top punch guide (29).

7. A rotary tablet press according to any one of claims 4 to 6, wherein said slider element (37) constitutes a second slider element connected to a first slider element (36).

8. A rotary tablet press according to any one of claim 3 to 7, wherein the spindle (33) is secured to a clamping device (35).

9. A rotary tablet press according to claim 2, wherein the turret includes a spindle extending in said axial direction through the bottom punch guide only in the position of use, and said quick separation means comprises release means for separating the top punch guide from the die disc and the die disc from the bottom punch guide and lifting means for lifting the top punch guide out of engagement with the die disc and the bottom punch guide to attain said removal position.

10. A rotary tablet press according to claim 9, wherein the re- lease means for separating the top punch guide from the die disc and the die disc from the bottom punch guide include bolts or a quick lock mechanism.

11. A rotary tablet press according to any one of the preceding claims, wherein the turret (12) furthermore comprises a number of guide pins (40) accommodated in bores (41,42,43) in the top punch guide (29), the die disc (15) and the bottom punch guide (30), respectively.

12. A rotary tablet press according to claim 11, wherein said guide pins (40) and said bores (41,42,43) are slightly conical.

13. A rotary tablet press according to any one of the preceding claims, wherein the quick separation means furthermore comprises a plurality of spring-loaded push pins (24) accommodated in the bottom punch guide (30), said spring-loaded push pins (24) being adapted to lift the die disc (15) slightly.

14. A rotary tablet press according to any one of the preceding claims, wherein the turret (12) furthermore comprises at least one alignment pin (22) accommodated in the bottom punch guide (30) and cooperating, in the position of use, with an alignment bore (23) provided in the die disc (15).

15. A rotary tablet press according to claims 13 and 14, wherein said spring-loaded push pins (24) are adapted to lift the die disc (15), in the removal position, to such an extent that the alignment bore (23) is lifted up over the alignment pin (22).

16. A rotary tablet press according to claim 1, wherein the quick separation means are adapted for allowing quick separation between the die disc (15") and the bottom punch guide (30") by release means and lifting means.

17. A rotary tablet press according to any one of the preceding claims, wherein the die disc has a reduced weight, preferably below 10 kg.

18. A rotary tablet press according to claim 17, wherein the material of the die disc is a lightweight metal or metal alloy.

19. A rotary tablet press according to claim 17 or 18, wherein the die disc is designed as a ring.

20. A rotary tablet press according to any one of claims 17 to 19, wherein the die disc is provided with a plurality of bores and/or milled profiles.

21. A rotary tablet press according to any one of the preceding claims, wherein the rotary tablet press furthermore comprises a die disc removal device in the compression section (6) of the housing.

22. A rotary tablet press according to claim 21, wherein said die disc removal device comprises a vertical pillar (60; 160) to which a swivel arm (61; 161) is connected pivotally.

23. A rotary tablet press according to claim 22, wherein said swivel arm (61) has a first and a second leg (62,63) adapted to be inserted below the die disc (15).

24. A rotary tablet press according to claim 22, wherein said swivel arm (161) has a substantially C-shaped leg (162) adapted to be inserted below the die disc (15).

25. A rotary tablet press according to claim 21, wherein said die disc removal device comprises a vertical pillar (70) to which a horizontal arm (71) is secured, and wherein a carriage (72) capable of translatory movement is connected to the horizontal arm (71), said carriage (72) being, in turn, connected to a first and a second leg (73,74) adapted to be inserted below the die disc (15).

26. A rotary tablet press according to claim 21, wherein said die disc removal device comprises a translatory carriage (170) connected to a stationary plate (52) in the compression section (6) by means of fittings (171), said translatory carriage (170) comprising a plurality of bearings (172) and guide plates (173) on either longitudinal side.

27. A method of exchanging at least one part of a rotary turret of a rotary tablet press, whereby the turret including the parts of a die disc, a top punch guide, and a bottom punch guide, is positioned in a compression section of a housing of the rotary tablet press in a position of use, said die disc being secured between said top punch guide and said bottom punch guide in the position of use, comprising the steps of: providing quick separation between the die disc and the top punch guide and/or between the die disc and the bottom punch guide in the compression section to attain a removal position, removing said at least one part from the compression section, and inserting a part into the compression section.

28. The method of claim 27, whereby the die disc is separated from at least the top punch guide in two steps including releasing the top punch guide from engagement with the die disc and lifting the top punch guide out of engagement with the die disc and the bottom punch guide.

29. The method of claim 28, whereby the turret includes a spindle extending through the top punch guide and defining an axial direction, the die disc and the bottom punch guide in the position of use, and the quick separation is provided by first releasing the spindle from engagement with the bottom punch guide and moving the spindle axially within the turret, and subsequently lifting the top punch guide and the spindle out of engagement with the die disc and the bottom punch guide to attain the removal position.

30. The method of claim 29, whereby the quick separation includes the further step of lifting the die disc slightly in the removal position.

31. The method of any one of claims 27 to 30, wherein the at least one part to be exchanged includes the die disc.

32. The method of claim 31, whereby the removal from and the insertion into the compression section of the die disc is carried out manually.

33. The method of claim 31, whereby the removal from and the insertion into the compression section of the die disc is carried out by means of a die disc removal device.

34. The method of claim 27, whereby the die disc is separated from the bottom punch guide in two steps including releasing the top punch guide and the die disc from engagement with the bottom punch guide and lifting the top punch guide and the die disc out of engagement with the bottom punch guide.

35. The method of any one of claims 27 to 34, wherein the at least one part to be exchanged includes the bottom punch guide.

36. The method of any one of claims 27 to 35, wherein the at least one part to be exchanged includes the top punch guide.