US3045641A - Apparatus for color-coding tablets - Google Patents

Description

July 24, 1962 F. e. ODDO APPARATUS FOR COLOR-CODING TABLETS 2 Sheets-Sheet 1 Filed April 13, 1959 INVENTOR Franli' G. Oddo Jam/5% ATTORNEYS July 24, 1962 F. G. ODDO APPARATUS FOR COLOR- CODING TABLETS 2 SheetsSheet 2 Filed April 15, 1959 INVENTOR FILULK G. 001F310 ATTORNEYS 3 045 641 APPARATUS FOR GOLbR-CODIN G TABLETS Frank G. Oddo, Midland Park, N.J., assignor to Chas. Pfizer & Co., Inc, New York, N.Y., a corporation of Delaware Filed Apr. 13, 1959, Ser. No. 805,773 Claims. ((11. 118-16) This invention relates to an apparatus and method for coating tablets, and more particularly to an apparatus and method for coating pharmaceutical tablets.

In the manufacture of pharmaceutical tablets, it is customary to apply a coating to the tablet surface. Such coatings serve a number of purposes. For example, they help to identify the manufacturer and the content of the tablets, for safety and convenience, and have, as well, a decorative effect. In some instances they may also serve to mask objectionable taste or to protect the tablets from deterioration by exposure to atmospheric conditions. Such coatings are ordinarily applied to the tablets while they are tumbled in a rotating vessel. However, it is well known that such coating operations are slow, and require careful supervision by skilled operators.

In order that such tablets be readily distinguishable from one another, dyes or pigments are often incorporated in the coating. The number of easily differentiated colors is limited, however. Manufacturers have therefore sometimes resorted to the alternative measure of providing multilayer tablets, usually prepared from two powders of different color. This method greatly extends the range of available tablet effects, thereby simplifying the problem of distinguishing between different products, and in addition provides a particularly pleasing appearance. However, the preparation of multilayer tablets is a difficult procedure, necessitating the use of special tabletting equipment, which, because of the extra operations involved, requires careful supervision and entails sharply reduced production capacity.

Accordingly, it is an object of this invention to provide a novel apparatus for color-coding tablets.

Another object is to provide such an apparatus for automatically color-coding tablets at a high rate of speed and with a minimum of supervision.

A further object is to provide an apparatus for imparting to tablets the attractive appearance of multilayer tablets.

Still another object is to provide such an apparatus which is relatively simple, economical and dependable in operation.

In accordance with this invention, tablets are colorcoded by impressing them deeply into a very soft surface covered with a coating substance. An apparatus for automatically color-coding tablets at a relatively high rate of speed includes a conveyor belt for carrying the tablets beneath a rotating resilient roller. Means are provided for applying a continuous layer of coating substance to the surface of this roller. In addition, an adjustment means is furnished for varying the depth of penetration of the tablets into the surface of the roller, so that a variety of effects may be achieved.

Novel features and advantages of the present invention will be apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings, in which similar reference characters refer to similar parts and in which:

FIG. 1 is a view in elevation of one embodiment of the present invention.

FIG. 2 is a fragmentary plan view of a portion of the embodiment shown in FIG. 1.

FIG. 3 is a cross sectional view, taken along the line 3-3 and looking in the direction of the arrows, of the portion shown in FIG. 2.

FIG. 4 is an enlarged cross-sectional view, taken along the line 44 and loking in the direction of the arrows, of another portion of the embodiment shown in FIG. 1.-

=FIG. 5 is an enlarged elevational view of another portion of the embodiment shown in FIG. 1.

FIG. 6 is a cross-sectional view, taken along the line 66 and looking in the direction of the arrows, of the portion shown in FIG. 5.

FIG. 7 is an enlarged view, partially in section, of another embodiment of the portion shown in FIG. 4.

FIGS. 8, a, b, c, d, e and f are side elevational views of tablets coated by the apparatus and method of the present invention.

FIG. 9 is a plan View of an engraved tablet colored by the apparatus and method of the present invention.

In FIG. 1 is shown an apparatus 10 for color-coding tablets '12 including a conveyor 14, for example, of the endless-belt type including a series of compartmental units 16. Each unit, for example, is a bar 16 incorporating a series of tablet carriers 18. Bars '16 are articulated upon an endless conveyor belt, for example, of the sprocket chain variety.

A tablet-feeding means 20 is mounted adjacent one end of conveyor 14 for filling tablet carriers 18 with tablets. Feeding means 20 includes, for example, a loading hopper 22, a transfer drum 24 and a loading drum 26. A rotating cylindrical loading brush 28 is mounted adjacent the surface of transfer drum 24 near the outlet from hopper 22 for urging tablets 12 into radial pockets 30 on the surface of transfer drum 24.

Transfer drum 24 is mounted parallel and tangent to loading drum 26. Intermeshing gears 25 and 27, mounted concentrically with these drums, provide the proper rotation and are in turn driven through pinions 34 by change gear 31 mounted coaxially with conveyor sprocket 32. This synchronizes radial pockets 30 on transfer drum 24 with tablet-shaped pockets 36 spaced about the periphery of loading drum 26. Pockets 36 are synchronized in turn with successive pockets 38 in tablet carriers 18 of conveyor belt 14. A tablet 12 is, accordingly, transferred from each radial pocket 30 on drum 24 to each pocket 36 on drum 26; and from each pocket 36 a tablet is subsequently deposited in each pocket 38 of conveyor 14 as they pass close to each other at their point of substantial tangency. Arcuate retaining plates 40 and 42 are mounted adjacent the outer periphery of transfer drum 24 and loading drum 26, respectively, to maintain tablets 12 inserted within pockets 30 and 36 as they are rotated upside down to the respective transfer positions.

A rotating cylindrical roller 44 is mounted adjacent the path of travel of conveyor 14 which is substantially longitudinal beyond loading drum 26. Roller 44, shown in FIG. 6, consists of an axially recessed core 45, preferably of metal, upon which is molded a surface layer 47 of a soft, resilient substance. Layer 47 is made, for example, of natural or synthetic rubber, or a plastisol of vinyl chloride polymer together with a plasticizer, and preferably has a hardness of from about 10 to about 35 standard units as measured on the Durometer A scale. Layer 47 may have a thickness ranging from about 0.2 inch to an inch or more, but will in any case be at least as thick as the tablets it is desired to coat, for reasons described hereinbelow. Roller 44 is concentrically mounted on shaft 62 by set screws 49, so that roller and shaft rotate in unison.

A continuous uniform layer of a liquid coating substance 46 is transferred from a trough 48 to the surface of roller 44 by a roller 50 and tangent rotating rollers 51. Roller 50 will ordinarily be entirely of metal, whereas rollers 51 will have a resilient surface, for example, of rubber having a 'Durometer A hardness of from about 60 to about 70. Resilient roller 44 and rollers 5t and 51 are rotated by coaxially mounted intermeshing spur gears 53, propelled by conveyor sprocket 52 through sprocket chain 54 and coaxial sprocket-and-gear 56.

Power is supplied to sprocket 52 from motor 58 by belt 60.

Roller 44 is mounted at a predetermined height so that as the tablets pass beneath it on conveyor 14 they are deeply impressed into the resilient roller surface. As a result, coating substance 46 is transfered from the roller to the tablet surface. An adjustment for controlling the degree of penetration into the roller is provided, for example, by means illustrated in detail in FIGS. and 6. Roller shaft 62 is journaled in slotted bearing blocks 64 made, for example, of brass which ride between frame members 66. Each bearing block is supported from beneath by a helical spring 68 securely positioned in frame recess 70. The vertical position of each block 64, and hence of roller 44, is adjustable by means of a cap bolt 72 which is threaded through a bearing plate 74 secured to frame members 66 by bolts 76.

A variety of coating substances are available for use with the apparatus and method of the present invention. For example, colors, including black or white, may be applied to the tablet by employing a dispersion of a pharmaceutic-ally acceptable ink or other dye or pigment in a volatile liquid. Often it will be desirable to incorporate a non-volatile film-forming substance in the formulation, in order to impart gloss or to provide a measure of protection to the tablet. Suitable substances for this purpose include natural and synthetic resins, such as pharmaceutical shellac, ethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, or mixtures of such substances. Other ingredients, including opacifiers, such as titanium dioxide, and plasticizers may also be included. The following formulations are given by way of example:

Formulation 1 Other formulations will readily occur to those skilled in the art.

Where colored coatings are applied, a variety of attrative multilayer effects may readily be obtained, depending on the depth of penetration of the tablet into the roller. With moderate penetration, color is applied only to the upper tablet face 78, and the appearance illustrated in FIG. 8d is obtained. If the tablet face bears an engraved marking, as in FIG. 9, the recessed characters will remain uncolored and will thereby be accentuated. Greater penetration leads to the application of a band of color extending around tablet rim 80, as shown in FIG. 8c. With sufficient penetration this band may be caused to extend, for example, about halfway down the tablet rim to achieve the effect illustrated in FIG. 8a. Thus, it will be appreciated that a tablet having the appearance and advantages of a multilayer tablet is obtained with surprising ease and at a greatly enhanced production rate.

The minimum thickness of resilient layer 47 necessary to achieve such penetration without crushing the tablet will, of course, vary with such factors as the tablet thickness and shape, as well as the precise compressibility of layer 47. It has been found, however, that a thickness at least equal to the greatest thickness of the tablet is essential for success.

The degree of adjustment in the height of roller 44 necessary to achieve the range of effects described is of the order of a fraction of an inch and accordingly does not interfere with maintenance of substantially tangent contact of roller 44 with adjacent roller 51. Furthermore, the adjustment is small enough to be absorbed by the gear lash, requiring no alteration in the gear train which drives the rollers.

A preferred form of tablet carrier 18, fabricated, for example, of hardened steel, and pictured in FIGS. 2, 3 and 4, includes a lower stern portion 82 and a head 84 having upon its upper surface a shallow cup-shaped depression or pocket 38. An axial recess 86 extends from pocket 38 through head 84 and terminates within stem 82. Head 84 is divided into four tablet-gripping jaw portions 88 by a pair of vertical slots 90 which pass through the vertical axis of carrier 18 substantially at right angles to each other and extend into shaft 82. Recess 86 and slots '90 provide a limited degree of flexibility to jaws 88 with respect to stem 82, furnishing means for releasably gripping a tablet as hereinafter described.

Carrier head 84 has the shape of an inverted conical frustrum, the sides tapering, for example, about 7 from the vertical. A matching bevel is formed on the inner surface of hardened steel bushing 92 mounted in upper large-bore vertical recess 96 in bar 16. Bushing 92 rests on shoulder 94 created by the junction of recess 96 and concentric small-bore vertical recess 98 which together extend through bar 16. Carrier 18 is mounted in bushing 92 with stem 82 extending [downwardly through and beyond recess 98 in freely movably fit therewith. A helical spring 100 about the lower extremity of stem 82 is retained by a split spring washer 102, for example, of the type known as a Tru-arc washer, mounted in a groove adjacent the lower end of stem 82. Spring 100 exerts pressure on lower surface 104 of bar 16, drawing tapered head 84 into bushing 92 and thereby causing arcuate ridges 106 on jaws 88 to grip and hold the tablet in pocket 38.

Where the above-described tablet carrier is employed, special means, illustrated, for example, in FIG. 1, are provided for accepting and releasing the tablet. Cam 108 is adjustably mounted with its uppermost surface beneath the point of approximate tangency between loading drum 26 and conveyor 14 in such position that as carrier 18 approaches the loading drum stem 82 impinges on the cam surface. Further travel of conveyor 14 causes a resultant vertical force to be applied to stem 82, which rides upward on the cam, compressing spring 100 and raising carrier head 84 out of bushing 92. As shown in FIG. 3 jaws 88 then spread to their equilibrium positions, permitting a tablet to be deposited from loading drum 26 in pocket 38. As conveyor 14 continues its advance, stem 82 rides downward under the influence of spring 100 and ridges 106 firmly grip the tablet rim. The tablet is carried in this position past resilient roller 44, as detailed in FIG. 4, and the coating is applied as previously described. Further travel brings the tablet around to the underside of the machine while the coating dries. It may sometimes be desirable to acceleratedrying by heating the tablets after they are coated and before discharge from the machine. This may be accomplished, for example, by subjecting the tablets to radiation from infrared lamps mounted above their path of travel. Forced-air circulation may also be provided if desired, to assist in removal of solvent vapors. At an appropriate position on the underside of the machine a second cam 110 releases the tablet to drop to a collecting container, not shown.

Alternatively, as indicated in FIG. 1, cam 110 may transfer the inverted tablet to a tablet carrier 18A mounted on a second conveyor 14A synchronized with conveyor 14 and traveling parallel to and beneath it. Carrier 18A is raised by cam 110A at a point directly below cam 110 to accept and grip the tablet. The uncoated surface of the tablet is thus exposed and maybe colorcoded in the same manner previously described in connection with apparatus 10A including conveyor 14A and a coloring roller assembly 200A designated by schematic rectangle 200A which is similar in all respects to those portions of apparatus 10 enclosed Within rectangle 200 In this Way, the same or a different coating may be applied to the reverse side of the tablet to obtain the effects illustrated in FIGS. 8e and 1. Where each coating is applied to extend at least halfway down tablet rim 80 a completely coated tablet, as shown in FIG. 8b, results. It will be appreciated that, while the foregoing description relates to a single tablet carrier, normally a series of carriers will be arrayed in a row on bar 16. Up to a quarter million tablets per hour may be coated as described, with a minimum of supervision. In contrast, prior art methods relying upon the use of large coating pans require continual supervision by skilled operators to coat an average of about 5,000 tablets per hour,

An alternative embodiment of tablet carrier 18, shown in FIG. 7, comprises a lower stern portion 82 and a head 84 having a tablet-carrying pocket 38. Carrier 18 fits freely within a vertical recess extending through bar 16 and is retained by a spring washer 102. Adjustable cam 112 is provided at a position beneath resilient roller 44 in such position that when stem 82 impringes upon the cam the tablet carrier is raised a predetermined distance and the tablet is impressed into the roller surface. The tablet effects illustrated in FIG. 8a, and d may be obtained by small adjustments in the height of cam 1 12. Since the carrier shown in FIG. 7 does not grip the tablets, they spill off the conveyor as it reaches the end of its horizontal travel and are collected in an appropriate container.

What is claimed is:

1. An apparatus for color-coding tablets comprising a cylindrical roller having a soft resilient surface, conveyor means, a stationary frame, said conveyor means including a plurality of carriers, said carriers including smoothlysurfaced gripping means for securely grasping said tablets, said conveyor means being mounted upon said frame, support means mounting said cylindrical roller upon said frame adjacent the path of movement of said carriers to cause tablets grasped by said carriers to contact said soft resilient surface of said cylindrical roller, tablet feeding means operatively associated with said conveyor means for inserting said tablets within said carriers before they carry said tablets into contact with said roller, drive means mounted upon said frame and connected to motivate said conveyor and said roller, means for dispensing a coloring liquid to said roller, actuating means operatively connected with said carriers for opening said gripping means prior to receiving said tablets and after said tablets have contacted said roller for securely grasping said tablets in said carriers before passing under said roller and subsequently discharging said tablets, and said support means being adjustable to cause said tablets to penetrate a predetermined distance within said soft resilient surface thereby coloring a corresponding predetermined area upon said tablets.

2. An apparatus as set forth in claim 1 wherein said resilient layer has a Durometer A hardness of from about 10 to about 35 Standard Units.

3. An apparatus as set forth in claim 1 wherein each of said carriers comprises a head including a smoothlycurved depression for receiving said tablets, said head incorporating a number of spring jaws, a stem connected to each of said heads, said conveyor means including slotted conveyor sections, said stems being inserted to slide within the slots in said sections, the outer surface of said heads being tapered inwardly toward said stems, resilient means urging said stems into said slots whereby the walls of said slots urge said jaws to grasp said tablets, and a cam surface being mounted in the path of movement in said stems for urging said stems in a direction to move said heads out of said slots for causing said jaws to release said tablets.

4. An apparatus as set forth in claim 3 wherein said resilient means comprises a coil spring reacting between said slotted sections and said stems.

5. An apparatus as set forth in claim 1 wherein a pair of said apparatus are mounted with their conveyors disposed adjacent each other, said tablets being fed to one of said apparatus for coloring one of their surfaces and subsequently to the other of said apparatus for coloring of their other surfaces, the conveyors of said pair of apparatus being disposed one above each other at a transfer position, and said actuating means being disposed at said transfer position for dropping said tablets from one of said conveyors onto the other to permit the uncolored portion grasped in the first apparatus to be colored in the second apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 229,785 Whitney July 6, 1880 716,788 Thomson Dec. 23, 1902 1,115,426 Green Oct. 27, 1914 1,960,456 Robb May 29, 1934 2,182,068 Clark Dec. 5, 1939 2,352,773 Davis July 4, 1944 2,590,051 Spain Mar. 18, 1952 2,642,821 Hettinger June 23, 1953 2,663,269 Kloes Dec. 22, 1953 2,738,761 Gerwe Mar. 20, 1956 2,747,541 Chew May 29, 1956 2,931,292 Ackley Apr. 5, 1960 2,946,298 Doepel et a1. July 26, 1960 FOREIGN PATENTS 523,661 Canada Apr. 10, 1956 686,243 Great Britain Jan. 21, 1953 689,612 Great Britain Apr. 1, 1953

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