Miniaturized tablet coating apparatus and method

Abstract

A method is provided for coating tablets on-demand in a miniaturized coating apparatus. A supply of tablets are provided, each having dimensions and a mass. The supply of tablets together has a total number, a total mass and a total volume. In some aspects, specifications are selected for constructing a customized rotatable drum based on tablet dimensions, tablet number, total mass, total volume, physical and / or chemical properties of coating material(s) to be applied to the tablets, or a combination thereof. In some embodiments, the rotatable drum may be formed by 3D printing.

Description

MINIATURIZED TABLET COATING APPARATUS AND METHODCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit to U.S. Provisional Application No. 63 / 656,064, filed June 4, 2024, which is incorporated by reference herein in its entirety.BACKGROUND

[0002] One conventional tablet coating machine has a housing containing a rotatable drum with frustro-conical sides. The periphery of the drum is perforated to allow air to flow through a bed of tablets disposed in the drum. The tablets are loaded into the drum through an opening disposed in a plane perpendicular to the axis of the rotation of the drum. A spray gun is mounted from a non-rotatable part of the machine and has a nozzle positioned to direct the desired coating material towards tablets disposed in the drum. An open face of a suction shoe is disposed on the outside of the drum adjacent the periphery of the drum. Rotation of the drum in conjunction with the action of the airflow and any optional mixing means disposed in the drum generates a circulation of the bed of tablets so that an even coating is built up on all the tablets in the drum over a prescribed period of time.

[0003] The aim of such a device is to achieve a desired coating thickness on a given quantity of tablets (often measured in terms of weight gain) as efficiently as possible, where efficiency is measured in terms of the coating time and the efficient utilization of coating material, e.g., minimum wastage. Existing machines are designed for optimum performance with a specific quantity of tablets. Operating a machine at a different load than the recommended load tends to reduce coating efficiency, especially when coating batches smaller than the recommended batch size.

[0004] Morrow et al. U.S. Patent 6,129,038 discloses a tablet coating machine featuring a drum having an axially adjustable wall portion. The volumetric capacity of the drum may be adjusted to provide a desired tablet depth for a quantity of tablets being processed.

[0005] While Morrow ’038 may allow for a certain extent of customization to accommodate different tablet batch sizes, it would be desirable to develop a coating apparatus for coating tablets on-demand where multiple features of the coating pan are customizable, for example to allow for processing varying batch sizes, tablet sizes, coating materials,and / or other parameters. It would be particularly desirable to develop an apparatus that is miniaturized and particularly well suited for coating smaller batches of tablets on demand, such as in a retail or hospital pharmacy or clinical setting.SUMMARY

[0006] In one aspect, a method is provided for coating tablets in a miniaturized coating apparatus. The apparatus includes a drum configured to rotate about an axis. The drum has a main body having a width, an interior circumferential surface and an interior volume. The drum also has a first end portion having an opening to provide access to the interior volume, and a plurality of baffles spaced apart from each other and extending along the interior circumferential surface. Perforations are disposed along at least a portion of the main body.

[0007] A predetermined number of tablets are inserted into the interior volume of the drum. The tablets together define a tablet bed having a maximum depth D extending from a point along the interior circumferential surface toward the axis. The drum has a first radius Ri and the opening has a second radius R2 that, together with the tablet bed maximum depth D, satisfy the equation:(Ri - R2) > D

[0008] A coating material is applied onto the plurality of tablets while rotating the drum and supplying air to the drum via an air inlet. The baffles are configured to induce tumbling of the tablets as the drum is rotated.

[0009] In another aspect, a method is provided for coating tablets on-demand in a miniaturized coating apparatus. A supply of tablets are provided, each having dimensions and a mass. The supply of tablets together has a total number, a total mass and a total volume. Specifications are selected for constructing a customized rotatable drum based on tablet dimensions, tablet number, total mass, total volume, physical and / or chemical properties of coating material(s) to be applied to the tablets, or a combination thereof.

[0010] In some embodiments, the rotatable drum may be formed by 3D printing. The rotatable drum has a main body having a width, an interior circumferential surface and an interior volume; a first end portion having an opening to provide access to the interior volume;a plurality of baffles spaced apart from each other and extending along the interior circumferential surface; and perforations disposed along at least a portion of the main body.

[0011] The rotatable drum may be removably attached to a drive shaft operatively coupled to a motor configured to rotate the drum about an axis. The supply of tablets is inserted into the interior volume of the rotatable drum. The inserted tablets together defining a tablet bed. A coating material is discharged onto the supply of tablets while rotating the drum and supplying air to the drum via an air inlet. The baffles may be configured to induce tumbling of the tablets as the drum is rotated.

[0012] In yet another aspect, a miniaturized tablet coating apparatus is provided. The apparatus has a drum constructed of a 3D printable material and which is configured to rotate about an axis. The drum has a main body having an interior volume, first and second end portions spaced from each other by a first width. The drum also has an interior circumferential surface having first and second edges spaced from each other by a second width that is less than the first width. First and second angled portions extend from the first and second edges of the interior circumferential surface to the first and second end portions, respectively. Perforations are disposed along at least a portion of the main body. An access area extends from the first end portion and has an opening to provide access to the interior volume. A plurality of baffles are spaced apart from each other and extend along the second width.

[0013] A motor has a drive shaft removably connected to the drum for rotating the drum about the axis. A coating applicator is configured to apply a coating material onto tablets contained in the interior volume. An air supply is configured to deliver air into the drum via an air inlet. A controller may be configured to control airflow, drum rotation and operation of the coating applicator.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete understanding of the present invention and certain advantages thereof may be acquired by referring to the following detailed description in consideration with the accompanying drawings, in which:

[0015] FIG. 1 schematically illustrates a miniaturized tablet coating apparatus in accordance with one or more aspects;

[0016] FIG. 2 schematically illustrates a drum containing a tablet bed in accordance with one or more aspects;

[0017] FIGS. 3A-3C show a rotatable drum in accordance with one embodiment, with FIG. 3 A showing a perspective view, FIG. 3B showing a cross-sectional view and FIG. 3C showing an exploded cross-sectional view of a baffle;

[0018] FIG. 4 shows a rotatable drum in accordance with another embodiment;

[0019] FIGS. 5 A and 5B show a rotatable drum in accordance with another embodiment, with FIG. 5A showing a perspective view and FIG. 5B showing a cross-sectional view;

[0020] FIGS. 6 A and 6B show a rotatable drum in accordance with another embodiment, with FIG. 6A showing a perspective view and FIG. 6B showing a cross-sectional view;

[0021] FIGS. 7A-7C show a rotatable drum in accordance with another embodiment, with FIG. 7A showing a perspective view, FIG. 7B showing a cross-sectional view and FIG. 7C schematically showing an end insert for the drum;

[0022] FIGS. 8 A and 8B show a rotatable drum in accordance with another embodiment, with FIG. 8A showing a perspective view and FIG. 8B showing a cross-sectional view;

[0023] FIGS. 9A-9F show a rotatable drum in accordance with yet another embodiment, with FIG. 9A showing a perspective view, FIG. 9B showing a cross-sectional view, FIGS. 9C and 9D showing perspective views with mating sections separated, and FIGS. 9E and 9F showing a cross-sectional views with a coating nozzle inserted;

[0024] FIG. 10 is a cross-sectional view of a rotatable drum in accordance with one or more aspects;

[0025] FIG. 11 is a perspective view of an end surface of a rotatable drum that is configured for receiving a drive shaft in accordance with one or more aspects;

[0026] FIGS. 12A and 12B depict examples of structure that may be used to secure a drive shaft to the rotatable drum, with FIG. 12A showing a threaded rod using a single point of attachment and FIG. 12B depicting a 6-hole connector;

[0027] FIG. 13 shows a cross-sectional view of a rotatable drum in accordance with another embodiment;

[0028] FIG. 14 shows a cross-sectional view of a rotatable drum in accordance with yet another embodiment;

[0029] FIG. 15 shows a cross-sectional view of a rotatable drum in accordance with still another embodiment;

[0030] FIGS. 16A-16C illustrate an example of a non-cylindrical drum in accordance with another embodiment, with FIG. 16A showing a perspective view and FIGS. 16B and FIG. 16C showing cross-sectional views;

[0031] FIGS. 17 A and 17B show an example of a rotatable drum having rectangular baffles, with FIG. 17A showing a perspective view and FIG. 17B showing a cross-sectional view;

[0032] FIGS. 18A and 18B show an example of a rotatable drum having semicircular baffles, with FIG. 18A showing a perspective view and FIG. 18B showing a cross-sectional view;

[0033] FIGS. 19A and 19B show an example of a rotatable drum having irregularly shaped baffles, with FIG. 19A showing a perspective view and FIG. 19B showing a cross- sectional view;

[0034] FIGS. 20A and 20B show another example of a rotatable drum having irregularly shaped baffles, with FIG. 20A showing a perspective view and FIG. 20B showing a cross- sectional view; and

[0035] FIG. 21 shows a perspective view of an example of a rotatable drum having curved baffles.DETAILED DESCRIPTION

[0036] The present invention is directed to a miniaturized tablet coating apparatus and to methods of coating tablets on-demand using the same.

[0037] Terms not specifically defined herein have their accepted scientific and medical meaning as would be understood by persons of ordinary skill in the art.

[0038] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0039] As used herein, the term “optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not occur.

[0040] As used herein, the term “about” when used before a numerical designation, e.g., temperature, time, amount, concentration, and such other, including a range, indicates approximations which may vary by ( + ) or ( - ) 10%, 5%, 1%, or any subrange or subvalue there between. Preferably, the term “about” when used with regard to a value means that the value may vary by + / - 5%.

[0041] As used herein, the term “comprising” or “comprises” is intended to mean that the compositions and methods include the recited elements, but not excluding others.

[0042] As used herein, the term “consisting essentially of’ when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination for the stated purpose. Thus, a composition consisting essentially of the elements as defined herein would not exclude other materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed invention.

[0043] As used herein, the term “consisting of’ shall mean excluding more than trace elements of other ingredients and substantial method steps. Embodiments defined by each of these transition terms are within the scope of this invention.

[0044] The term “drum,” sometimes also referred to as a “pan,” as used herein, refers to a rotating device, which may be cylindrical and may include one or more tapered portions and may be configured or designed for use in a coating device for applying a coating or layer on one or more tablets. The drum may be configured to tumble tablets, such that the coating may be evenly applied to the one or more tablets. The drum may include one or more openings for receiving the tablets and / or a coating application device, such as a spraying device, which can be in the form of a nozzle, for dispensing a coating on the tablets.

[0045] The terms “miniature,” “miniaturized” and similar terms, when used herein with reference to a coating apparatus, refer to a rotatable drum whose internal volume is less than or equal to 4 liters (L). A coating apparatus is considered “ultra-miniaturized” when the internal volume of its drum is less than or equal to about 0.5 L.

[0046] The term “rotation axis,” unless otherwise clear from context, refers to the imaginary line about which an object rotates. In the case of the drum, the rotation axis may also be referred to as the z-axis, around which the drum rotates in a revolution from 0 to 360 degrees for any desired number of revolutions. The rotation axis may be, but is not necessarily parallel to a plane on which the coating device rests. For example, the rotation axis may be inclined slightly so as to concentrate tablets to one side of the drum.

[0047] The term “baffles,” as used herein, refers to raised sections, which may be wall or platelike features, which in certain examples may be positioned within the drum and may be attached or fixed to an inner surface of the drum. In certain examples, baffles may be configured or designed to agitate, lift, scoop and / or tumble the tablets during a coating process according to desired parameters and / or characteristics. For example, baffles may be configured to randomly orient the tablets to allow for a substantially even coating and a substantially even exposure to airflow.

[0048] The term “tablet,” as used herein, refers to a drug substance or combination of substances configured for treating, preventing, or diagnosing, or restoring or correcting modifying physiological functions (including placebos) which is a dry element. The dry element may be compacted to a solid, such as pills, or pellets, or filled into hard- or soft shelled capsules, and may include smaller forms such as minute portions, pieces, or fragments. These may further comprise a pharmaceutically acceptable excipient; such excipientsmay include one or more of a filler, binder, disintegrant, coloring agent, preservative, stabilizer, lubricant, dilutant, glidant, or the like. Unfilled capsules also may be coated by a miniaturized coating apparatus as described herein.

[0049] The term “heating element” may refer to any heating source or apparatus for heating and in certain examples may be used to increase the temperature of the airflow into the drum to aid in the application of a coating and in particular may assist in drying the coating to the tablets during and after application of the coating. Also, in certain examples, the heating element may include one or more controls for obtaining a desired temperature. In certain examples, the heating element may include a heating gun or equivalent structure.

[0050] The terms “tumbling” and “cascading” refer to causing tablets to rotate, stir, fall downwardly, randomly displace in multiple directions, and / or agitate within a drum. In one example, during the coating process the rotation of the drum may cause the tablets to randomly orient to assist with coating evenly all surfaces of the tablets with one or more layers. Also, the rotation of the drum may cause the tablets to randomly orient to assist with drying the coating by exposing each of the surfaces of the tablets to airflow. In certain examples, the airflow may be heated to increase the drying rate.

[0051] The term “coating,” as used herein, refers to an applied layer or covering over a tablet. The coating may provide, to the underlying tablets, one or more of enhanced mechanical strength, improved appearance, increased solubility, improved stability, an odor barrier, improved taste, and improved friability. In one example, the coating may control or modify drug release kinetics of the underlying tablets. In another example, the coating may create a uniform, planar layer to print an associated logo or identification. Further, the coating may provide environmental protection from, for example, moisture, temperature, and light. Additionally, the term “coating” may refer to the process of applying a coated layer or multiple coating layers. The coating may comprise compositions as described herein.

[0052] FIG. 1 schematically illustrates a miniaturized coating apparatus 1 in accordance with one or more aspects of the present disclosure. The apparatus 1 has a housing 10 containing a drum 20 configured to rotate about an axis. An air inlet 16 receives air from an air supply 12 which is directed into the drum 20 through perforations 21. An air outlet14 may include a fan (not illustrated) to create suction for exhausting air from the drum 20. The drum 20 has an opening 22 along an end surface to provide access to the interior volume, e.g., for inserting the tablets and a coating applicator such as a nozzle 30. In a typical operation, the nozzle 30 remains stationary as the drum 20 is rotated.

[0053] A heating element 34 may be provided for adjusting the temperature of the tablet bed as the coating material is applied to the tablets. Heating may be performed indirectly, such as by heating air from the air supply 12 as it approaches the air inlet 16, whereafter the tablet bed absorbs heat from the airflow. The tablet bed temperature may be adjusted, for example, to range from about 20 to about 80°C, often from about 30 to about 60°C. The target tablet bed temperature may be selected based on such criteria as the coating system chemical composition, coating system viscosity, coating system solids content, spray rate, batch size, airflow rate, drum rotation rate, tablet shape and size, and / or drum configuration.

[0054] A motor 36 has a drive shaft removably connected to the drum 20 for rotating the drum about its axis (see FIGS. 11, 12A and 12B and accompanying discussion below). A suitable controller 32 may be provided to receive input from sensors and control airflow, drum rotation and operation of the coating nozzle, for example. In some examples, the controller 32 may receive input from temperature sensors (not illustrated) positioned at the air inlet 16 and air outlet 14, and be configured to control operation of a fan (not illustrated) positioned at the air outlet 14 as well as rotation of the drum 20 via motor 36. In some examples, the controller 32 may be further configured to receive input from humidity sensors (not illustrated) positioned at the air inlet 16 and air outlet 14, and / or to control parameters such as airflow at the inlet air supply 12, the temperature of the air supply 12 via the heating element 34, and / or various other components such as the coating applicator 30 to spray coating material, a pump (not illustrated) to pump liquid to the coating applicator 30, a pressurized air supply (not illustrated) for atomization of coating material, a pressurized air supply (not illustrated) for controlling the pattern of the liquid spray, a mixer (not illustrated) to stir coating material before being pumped to nozzle 30, a balance (not illustrated) to measure remaining coating material, and / or a load cell (not illustrated) to measure the weight gain of tablets.

[0055] With reference to FIG. 2, a predetermined number of tablets may be inserted into the interior volume of the drum 20 via opening 22. In some examples, the number of tablets does not exceed about 100 and the total weight of tablets does not exceed about 150g. It should be understood, however, that there is no fixed upper limit on tablet number and weight, as these may vary depending on the tablet shape, tablet size and drum size used in the miniaturized coating apparatus.

[0056] The tablets together define a tablet bed 24 having a maximum depth D extending from a point along the interior circumferential surface toward the rotation axis. In some aspects, the drum 20 may have a first (inner) radius Ri and the opening 22 may have a second radius R2 that, together with the tablet bed maximum depth D, satisfy the equation:(Ri - R2) > D

[0057] Ordinarily, the maximum volume of the tablet bed 24 should not exceed about 40% of the internal volume of the drum 20. In some examples, the volume of the tablet bed 24 does not exceed about 35%, about 30% or about 25% of the internal volume. Also, during operation the tablet bed 24 should be spaced at least about 10 mm from the outlet of the spray nozzle 30. In some examples, the tablet bed 24 and spray gun 30 outlet are spaced from each other by at least about 12, 15, 18 or 20 mm.

[0058] As illustrated in FIG. 10, the drum depth A may be less than the drum’s total width w, which in some examples may also include angled portions 25. The term “angled portion” is used herein to refer to the portions of the drum 20 extending from the edges of the drum depth A outwardly to the end surfaces of the drum 20. The “angled” portions may be linear, curvilinear or of other non-linear shapes, e.g., as shown in FIGS. 13-15.

[0059] There is no particular minimum internal volume of the drum 20, with the minimum internal volume being limited only by functional considerations, notably the ability to insert a coating applicator 30. In one example of an ultra-miniaturized coating apparatus, the inner radius Ri may be 25 mm and drum depth A may be 26 mm, yielding an internal volume of (71 x (25 mm)2x 26 mm =) -51 cm3. This calculation assumes a 90 degree angled portion. Such calculation is provided merely by way of illustration, and it should be recognized that the drum 20 can change considerably in shape, as the drum does notneed a single straight line (cone shaped) angled portion, symmetrical angled portions, a cylindrical shape or even be symmetrical at all. Typically, the internal volume of the drum 20 ranges from about 0.05 to 4 L, and often from about 0.1 to about 3 L, about 0.2 to about 2.5 L, or about 0.3 to about 2 L.

[0060] With reference to FIGS. 3A and 3B, the drum 20 may have perforations 21 disposed along its entire circumferential surface or a portion thereof. The cross-sectional shape of the perforations 21 is not particularly limited and may be, for example, circular, rectangular, square, triangular, or various other geometric shapes. The maximum perforation size generally is limited by the tablet dimensions. That is, tablets may fall out of the drum 20 if the perforations 21 are larger than the tablet dimensions. Tablets intended for human administration typically range from about 1 to about 22 mm in length / diameter. Accordingly, in some examples the perforation size may range from about 0.75 to about 21.75 mm, depending on the tablet size being processed.

[0061] The drum illustrated in FIGS. 3A-3C may have a drum depth A of 40 mm, an internal drum radius of 82.5 mm, an opening 22 radius of 41.75 mm, an angled portion 25 at 70 degrees, a perforated hole diameter of 3 mm, a dense perforated hole pattern, a baffle 23 height of -5 mm and a baffle 23 width of 10 mm. As shown in FIG. 3C, the baffle 23 width may be defined by an angled portion 23a and quarter-circular side portion 23b. In this example, the radius of the quarter circle 23b is approximately 5mm, and thus approximately half of the baffle 23 is sloped and the other half a quarter-circle. The baffle dimensions and configuration may vary significantly. In some examples, the height of the baffles 23 may be selected to be approximately twice the length / diameter of the tablets being processed. In other examples, the height of the baffles 23 may be based on drum load or the drum radius Ri, for example.

[0062] In some aspects, the baffles 23 are configured to induce tumbling of the tablets as the drum 20 is rotated. To induce tumbling, the baffles 23 should have a sufficient width dimension, such as twice the length / diameter of the tablets being processed. See, e.g., FIG. 3C. Too narrow of a baffle width may cause tablets to slide down rather than tumble as the drum 20 is rotated. Larger baffles 23 generally induce tumbling more readily, but also effectively reduce the inner volume of the drum 20, which may limit the number of tablets that can be coated in a batch.

[0063] A number of features of the rotatable drum 20 may be customized for particular applications, non-limiting examples of which are illustrated in FIGS. 4-9. Among the features that may be customized are: drum depth A, internal drum radius Ri, opening 22 radius R2, configuration and angle of angled portion 25, width of perforations 21, perforated hole pattern, baffle height, baffle width, and baffle configuration.

[0064] The angle of the angled portion 25 may vary widely, as illustrated in the accompanying drawings, and is not particularly limited. Shallower angled portions 25 generally result in increased drum width w and internal volume for a given drum radius Ri. Conversely, steeper angled portions 25 generally yield a decreased drum width w and internal volume for a given drum radius Ri. Steeper angles, e.g., >65 or 70 degrees, also may help direct the tablets toward the coating (e.g., perforated) area of the drum 20 during operation.

[0065] The dimensions and configuration of the baffles 23 are not particularly limited and may vary significantly. In some examples, axially extending baffles 23 are angled at an angle ranging from about 30 to about 60°, or from about 35 to about 55°. In other examples, axially extending baffles 23 may be at a 90 degree angle. See, e.g., FIGS. 17A and 17B. In yet other examples, baffles 23 may have a curved / serpentine or other configuration. See, e.g., FIGS. 21A and 21B.

[0066] The radius R2 of the opening 22 also may vary widely. Usually, the radius R2 is at least about 5 mm to allow for insertion of the smallest available air / liquid hoses and threaded rod. The upper limit for the radius R2 is simply the drum radius Ri, although ordinarily the opening radius R2 should be less than the drum radius Ri to help prevent tablets from escaping the drum 20 as it is rotated.

[0067] FIG. 4 shows an example of a deeper drum 20 having a drum depth A of 120 mm, an internal drum radius of 82.5 mm, an opening 22 radius of 41.75 mm, an angled portion 25 at 70 degrees, a perforated hole diameter of 3 mm, a dense perforated hole pattern, a baffle height of -5 mm and a baffle width of 10 mm. The deeper drum 20 in this example may be used, for example, to accommodate a larger tablet bed 24.

[0068] FIGS. 5A-5B show an example of a rotatable drum 20 in which the angled portion 25 is disposed at an angle of 90 degrees. As seen in FIG. 5B, this configuration results in an overall narrower drum width w and decreased internal volume. In this example, theremaining specifications of the drum 20 may be the same as described above for the drum 20 depicted in FIGS. 3A-3C.

[0069] FIGS. 6A-6B show a rotatable drum 20 in accordance with another aspect, in which the angled portion 25 is disposed at an angle of 30 degrees. As seen in FIG. 6B, this configuration results in an overall greater drum width w and internal volume. In this example, the remaining specifications of the drum 20 may be the same as described above for the drum 20 depicted in FIGS. 3A-3C.

[0070] FIGS. 7A-7C show an example of a drum 20 in which the angled portion 25 is disposed at an angle of 10 degrees. The radius of the opening 22 at the terminus of the angled portion 25 is 75 mm. To prevent tablets from escaping the drum 20 during operation, an end wall 28 may be affixed to the drum 20. With reference to FIG. 7C, the end wall 28 may have an opening 22a that defines the radius R2 and provides access to the interior volume of the drum 20. As illustrated in FIG. 7B, the drum depth A, the baffle length h and the overall width w of the drum 20 may be three different values. In this example, the remaining specifications of the drum 20 may be the same as described above for the drum 20 depicted in FIGS. 3A-3C.

[0071] FIGS. 8A-8B show a rotatable drum 20 in accordance with another aspect and which may be adapted for coating 2 mm or larger tablets, for example. The drum 20 features perforations 21 configured as elongate slots having a length of 15 mm and a width of 2 mm. In this example, the remaining specifications of the drum 20 may be the same as described above for the drum 20 depicted in FIGS. 3A-3C.

[0072] Usually the opening 22 or 22a should be sufficiently large to allow insertion of the coating nozzle 30. In some examples, the opening 22 or 22a may have a significantly reduced radius, e.g., for use with a miniaturized spray gun 30. In some examples, the radius of the opening 22 or 22a may be reduced from 41.75 mm (as in FIG. 3 A and other embodiments) to 20 mm. FIGS. 9A-9F show an example of an ultra- miniaturized drum 20 featuring a drum depth A of 26 mm, an internal drum radius of 25 mm, an opening 22 radius of 5 mm, an angled portion 25 of 70 degrees, a perforated hole diameter of 1.75 mm, a dense perforated hole pattern, a baffle height of -2 mm and a baffle width of 4 mm.

[0073] The ultra- miniaturized drum 20 depicted in FIGS. 9A-9F may be used, for example, to coat a single 2 mm mini-tablet using a 25 mm x 25 mm (length / width) spray gun 30. Insertion of the spray gun 30 may be accomplished, for example, by constructing the drum 20 to have two mating sections 20a and 20b, as shown in FIGS. 9C and 9D. The mating sections 20a and 20b may be separated to allow insertion of the spray nozzle 30 through the rear of the drum 20, as shown in FIG. 9E. As shown in FIG. 9F, the spray nozzle 30 may be offset internally to allow for a 15 mm clearance from the tablet to be coated. Note that in FIG. 9F, the spray direction is coming out of the page.

[0074] FIGS. 13-15 show cross-sectional views of asymmetric / irregular shaped drums 20. FIG. 13 depicts a drum 20 having two sloped portions 25a and 25b on the right-hand side; where the left-hand side has a 90 degree angle with cutout 25c. FIG. 14 shows a drum 20 having an elegant spline 25a on the right-hand side and a random pattern of straight lines 25c on the left-hand side. FIG. 15 shows a drum 20 having a curved portion 25a on the right-hand side and random splines 25c on the left-hand side.

[0075] FIGS. 16A-16C illustrate an example of a non-cylindrical drum 20 having a generally triangular cross-section. As shown in FIG. 16C, the outside surfaces of the three sides may be generally planar and have a variable thickness, defining a more rounded interior circumference. The perforations 21 may extend along a portion of each of the three sides, with solid (non-perforated) comer areas 27 joining the perforated sides. The baffles 23 may be positioned along the interior of the sides and / or comer areas 27. An end wall 28 has an opening 22a to provide access to the interior volume.

[0076] FIGS. 17-21 show non-limiting examples of alternative baffle configurations. FIGS. 17A and 17B show axially extending baffles 23 having a rectangular cross-section. As shown in FIG. 17B, the edges of the baffles 23 are at a 90 degree angle relative to the interior circumferential surface of the drum 20. FIGS. 18A and 18B show axially extending baffles 23 having a semicircular cross-section. FIGS. 19A-19B and 20A-20B show examples of rotatable dmms 20 featuring axially extending baffles 23 having random or irregularly shaped cross-sections.

[0077] FIG. 21 shows an example of a rotatable drum 20 having curved baffles 23. Such a baffle pattern may have the effect of changing the tablet bed distribution, e.g., by pushing the tablets toward the back of the dmm 20.

[0078] In other examples of ultra-miniaturized drums 20, the angled portion 25 may be disposed at angles of 20 degrees or 10 degrees, which may yield configurations generally similar in appearance to those of FIGS. 6 and 7, respectively. Also, similar to the embodiment shown in FIGS. 7A-7C, the radius of the opening 22 at the terminus of the angled portion 25 may be made larger, e.g., 24 mm, with an end wall 28 affixed thereto having an opening 22a that defines the radius R2 and provides access to the interior volume of the drum 20.

[0079] As shown in FIG. 11, the end surface 26 of the drum 20 that is opposite the opening 22 or 22a may have a threaded hole 29 to allow attachment of a drive shaft to rotate the drum 20. For example, as shown in FIG. 12A, the hole 29 may receive a threaded rod 40 whose other end may be coupled to a drive shaft 44 via a shaft collar 42.

[0080] Various other techniques may be used to secure the drum 20 to the drive shaft 44, nonlimiting examples of which include a 6-hole connector 46, as depicted in FIG. 12B, which may be secured to the end surface 26 to receive the drive shaft 44. This type of connector 46 may provide a stronger connection than a single point of attachment. For example, offsetting the connection points from the axis of the drive shaft 44 may help prevent the threaded rod from unscrewing during rotation of the drive shaft, which may be prone to occur during high acceleration. Alternatively, a quick-release mechanism may be used that allows the drum to be clicked onto the drive shaft 44 and removed by pulling a release lever, similar to the mechanism used for a quick-release steering wheel in a racecar.

[0081] In some examples, the rotatable drum 20 may be formed by 3D printing. Specifications may be selected for constructing a customized rotatable drum 20 based on such variables as tablet dimensions, tablet number, total mass, total volume, physical and / or chemical properties of coating material(s) to be applied, or any combination thereof. The drum 20 may be constructed out of a single or multiple parts, whether formed by 3D printing or by other means. A monolithic construction may be advantageous in terms of simplicity, e.g., fewer parts and easier setup, and overall increased reliability. 3D printing allows for non-standard sizes and infinite possibilities of adjustment of the features of the drum (baffles, perforations, etc.). The non-standard sizing allows for varying tablet batch sizesto be coated, as a new drum may be printed as needed for processing a non-standard batch size.

[0082] The type of 3D printing technology that may be used is not particularly limited. Stereolithography (SLA) is well suited for printing small complex features and areas with substantial overhang. Other, non-limiting examples of 3D printing technologies include fused deposition modeling (FDM) and selective laser sintering (SLS). The materials that may be used with 3D printing are not particularly limited but should have sufficient thermal stability to withstand temperatures typically used to dry the tablets. For devices that currently are commercially available, SLA uses resins, while FDM and SLS employ plastic filaments and powders, respectively. A variety of 3D printing technologies and materials, including metals, that may be employed are described, e.g., in A. Jandyal et al. “3D printing - A review of processes, materials and applications in industry 4.0,” Sustainable Operations and Computers 3 (2022) 33-42. For additional details of 3D printing, see also N. Shahrubudin et al., “An Overview on 3D Printing Technology: Technological, Materials, and Applications,” Procedia Manufacturing, Vol. 35, 2019, 1286-1296; and N. Guo et al., “Additive manufacturing: technology, applications and research needs,” Front. Meeh. Eng. 8, 215-243 (2013). Non-widely available 3D printing technologies and materials also may be used as appropriate.

[0083] In some examples, the drum 20 may be printed using composite materials, or certain components may be printed using more than one material. For example, FDM may be used to print the outer surfaces of a component with a material that is different from the infill of the component. This may allow for a more durable part or a part that is better solvent resistant, for example. Other components in the overall apparatus may also be prepared using composite and / or multiple materials, and / or by 3D printing to achieve desired properties and function, including ease of assembly.

[0084] In some embodiments, a load cell (not illustrated) may be connected to the drum to measure weight gain of the tablets. The apparatus also may include an integrated stirrer and balance (not illustrated) to mix and measure the amount of remaining coating solution, respectively. These and / or other add-ons may yield a standalone device, versus a coating system that utilizes external components. An operator could simply insert a coating suspension (like a printer cartridge) to begin the coating process. In someexamples, a device may be configured to stop automatically upon achieving a desired weight gain, e.g., as measured by the load cell. Such a device may work well in a clinical setting, for example, where a limited number of tablets needs to be coated. Such a device may make coating tablets particularly easy for on-demand applications, such as in retailor other pharmacy-type settings and at clinical trial sites that may perform both drug product preparation and dose administration to patients.

[0085] The types of coatings that may be applied to tablets can vary widely. Some common examples of coating systems include polymers that are cellulosic based (e.g., hypromellose, hydroxypropyl cellulose, hydroxyethyl cellulose, and methylcellulose) or vinyl based (e.g., polyvinyl alcohol and PVA-PEG graft copolymer). Other examples include plasticizers that feature polyhydric alcohols, esters, fatty acids, and / or oils. Glycols, such as polyethylene glycol, also may be used as plasticizers. Some coating systems include pigments, such as dye, lake, or non- synthetic. Other examples include acrylics, such as methacrylic acid copolymers, are mostly used with modified (non- immediate) release film-coating formulations.

[0086] Functional coatings may, for example, modify or delay the drug release from a tablet. Coating systems may also may contain active pharmaceutical ingredient(s). Some simple coating technologies involve sugar coatings which use water to create the solution / suspension. Other examples use either aqueous or organic solvents for creating the coating system that is sprayed onto the tablets. Non-limiting examples of coating systems are described in A. N. Zaid, “A Comprehensive Review on Pharmaceutical Film Coating: Past, Present, and Future,” Drug Design, Development and Therapy, 2020:14, 4613-4623the disclosure of which is hereby incorporated by reference.

[0087] While the invention has been described with respect to specific examples, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques that fall within the spirit and scope of the invention as set forth in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method of coating tablets in a miniaturized coating apparatus comprising: a. providing a drum configured to rotate about an axis, the drum having: i. a main body having a width, an interior circumferential surface and an interior volume, ii. a first end portion having an opening to provide access to the interior volume, iii. a plurality of baffles spaced apart from each other and extending along the interior circumferential surface, and iv. perforations disposed along at least a portion of the main body; b. inserting a predetermined number of tablets into the interior volume of the drum, the inserted tablets together defining a tablet bed having a maximum depth D extending from a point along the interior circumferential surface toward the axis; wherein the drum has a first radius Ri and the opening has a second radius R2 that, together with the tablet bed maximum depth D, satisfy the following equation:(Ri - R2) > D; and c. applying a coating material onto the plurality of tablets while rotating the drum and supplying air to the drum via an air inlet, wherein the baffles are configured to induce tumbling of the tablets as the drum is rotated.

2. The method of claim 1, wherein each of the baffles extends axially along the interior circumferential surface.

3. The method of claim 1, wherein the main body has one or more angled portions extending from the first end portion toward the portion of the main body containing the perforations.

4. The method of claim 1, further comprising controlling a temperature of the tablet bed as the coating material is applied to the tablets.

5. The method of claim 4, wherein the temperature of the tablet bed is controlled by heating the air supplied to the air inlet.

6. A method of coating tablets on-demand in a miniaturized coating apparatus, the method comprising: a. providing a supply of tablets each having dimensions and a mass, wherein the supply of tablets together has a total number, a total mass and a total volume; b. selecting specifications for constructing a customized rotatable drum based on tablet dimensions, tablet number, total mass, total volume, physical and / or chemical properties of one or more coating materials to be applied to the tablets, or a combination thereof; c. forming the rotatable drum by 3D printing, the rotatable drum comprising: i. a main body having a width, an interior circumferential surface and an interior volume, ii. a first end portion having an opening to provide access to the interior volume, iii. a plurality of baffles spaced apart from each other and extending along the interior circumferential surface, and iv. perforations disposed along at least a portion of the main body; d. removably attaching the rotatable drum to a drive shaft operatively coupled to a motor configured to rotate the drum about an axis; e. inserting the supply of tablets into the interior volume of the rotatable drum, the inserted tablets together defining a tablet bed; and f. discharging a coating material onto the supply of tablets while rotating the drum and supplying air to the drum via an air inlet, wherein the baffles induce tumbling of the tablets as the drum is rotated.

7. The method of claim 7, wherein the rotatable drum has a first radius Ri, the opening has a second radius R2 and the tablet bed has a maximum depth D extending from a point along the interior circumferential surface toward the axis, wherein Ri, R2 and D together satisfy the following equation:(Ri - R2) > D.

8. The method of claim 7, wherein each of the baffles extends axially along the interior circumferential surface.

9. The method of claim 7, wherein the main body has one or more angled portions extending from the first end portion toward the portion of the main body containing the perforations.

10. The method of claim 7, further comprising controlling a temperature of the tablet bed as the coating material is applied to the tablets.

11. The method of claim 10, wherein the temperature of the tablet bed is controlled by heating the air supplied to the air inlet.

12. The method of claim 7, wherein the rotatable drum is formed by stereolithography (SLA).

13. The method of claim 7, wherein the rotatable drum is formed by fused deposition modeling (FDM).

14. The method of claim 7, wherein the rotatable drum is formed by selective laser sintering (SLS).

15. The method of claim 7, wherein the rotatable drum is formed by 3D printing a metal.

16. A miniaturized tablet coating apparatus comprising: a. a drum constructed of a 3D printable material and configured to rotate about an axis, the drum having: i. a main body having an interior volume, first and second end portions spaced from each other by a first width, an interior circumferential surface having first and second edges spaced from each other by a second width that is less than the first width, and first and second angled portions extending from the first and second edges of the interior circumferential surface to the first and second end portions, respectively; ii. perforations disposed along at least a portion of the main body, iii. an access area extending from the first end portion, the access area having an opening to provide access to the interior volume, andiv. a plurality of baffles spaced apart from each other and extending along the second width; b. a motor having a drive shaft removably connected to the drum for rotating the drum about the axis; c. a coating applicator configured to apply a coating material onto tablets contained in the interior volume; d. an air supply configured to deliver air into the drum via an air inlet; and e. a controller configured to receive sensor signals and control airflow, drum rotation and operation of the coating applicator.

17. The miniaturized tablet coating apparatus of claim 16, wherein each of the baffles extends axially along the interior circumferential surface.

18. The miniaturized tablet coating apparatus of claim 16, further comprising a heating element for adjusting a temperature of tablets contained in the interior volume of the drum.

19. The miniaturized tablet coating apparatus of claim 18, wherein the heating element is configured to heat the air supplied to the air inlet.

20. The miniaturized tablet coating apparatus of claim 19, wherein the controller is configured to control operation of the heating element.

21. The miniaturized tablet coating apparatus of claim 16, wherein the second end portion of the main body has an aperture configured for receiving a threaded rod for attachment to the drive shaft of the motor.

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